The present invention relates to an epoxidized block copolymer suitable for use in modifiers or modifier auxiliaries for rubbery or resinous polymers, adhesives, sealants, etc.
A block copolymer formed from a vinyl aromatic hydrocarbon compound and a conjugated diene compound and a hydrogenation product of the block copolymer are transparent, have the same elasticity as that of a vulcanized natural or synthetic rubber at ordinary temperatures even when it is not vulcanized and exhibits the same processability as that of a thermoplastic resin at high temperatures. Therefore, the above block copolymer is widely utilized in the field of various modifiers, adhesives, etc. To improve further the above performance of the block copolymer, the inventors have made many proposals for the use of an epoxidized block copolymer obtained by epoxidizing unsaturated carbon bonds attributed to the diene block of a block copolymer or a hydrogenation product thereof.
JP-A-5-125197 (1993) describes a (radiation)crosslinkable adhesive composition containing a polybutadiene block polymer provided with epoxy functionality and further describes that the obtained polymer can be melt-processed before it is crosslinked and has a high gel content after it is crosslinked to thereby improve the heat and solvent resistances.
However, it is described that the epoxidized block copolymer of this prior art can be one containing both epoxide and hydroxyester groups, attributed to partial opening of the epoxy ring, when the epoxidation reaction is conducted in the presence of an acid catalyst. Further, even if an epoxidized block copolymer having a low gel content is obtained before the crosslinking, further gelation may occur during the subsequent molding through heat melting. This gelation causes a drawback that moldability is gravely deteriorated.
The present invention provides an epoxidized block copolymer (E) obtained by epoxidizing a block copolymer (C) comprising a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound and a polymer block (B) composed mainly of a conjugated diene compound or a hydrogenation product (D) thereof, meeting at least one of the following requisites:
(1) having a molar ratio (R) of existing hydroxyl to existing epoxy ranging from 0.001 to 0.1, the molar ratio (R) being represented by the formula:
R=[hydroxyl]/[epoxy]
wherein [hydroxyl] represents the mole number of hydroxyl groups contained per unit weight of the epoxidized block copolymer and [epoxy] represents the mole number of epoxy groups contained per unit weight of the epoxidized block copolymer;
(2) having a gel content of not greater than 5% by weight; and
(3) having a chloride (chlorine) ion content of not greater than 7 ppm.
Preferably, the epoxidized block copolymer (E) is provided, further meeting at least one of the following requisites:
(4) having an acid value of not greater than 10 mgKOH/g;
(5) having a residual organic solvent content of not greater than 5000 ppm; and
(6) having an epoxy equivalent of 140 to 2700.
It is preferred that the hydrogenation product, being hydrogenated in part, have a hydrogenation ratio of 20 to 99% in the block (B) unit; that the molar ratio (R) range from 0.001 to 0.05; that the acid value be not greater than 5 mgKOH/g; and that the gel content range from 0.0001 to 1% by weight per copolymer unit.
Moreover, the present invention provides a process for producing an epoxidized block copolymer, which comprises the steps of:
(1) mixing the above block copolymer (C) or a hydrogenation product (D) thereof with an organic solvent so as to obtain an organic solvent solution or organic solvent slurry having a polymer concentration of 5 to 50% by weight;
(2) epoxidizing unsaturated carbon bonds contained in the above polymer block (B) with use of an epoxidizing agent in the organic solvent solution or organic solvent slurry; and
(3) evaporating off the organic solvent from the reaction mixture to thereby obtain an epoxidized block copolymer.
The epoxidation reaction mixture obtained in the step (2) in the form of a solution or slurry can be washed with water and/or neutralized so that the acid value of the solution or slurry may not exceed 5 mgKOH/g prior to being fed to the step (3). Thus, the above epoxidized block copolymer can be obtained. In particular, the epoxidized block copolymer which meets at least one of the above requisites (1), (2) and (3) can be obtained.
In the process of the present invention, a phenolic stabilizer and/or a phosphorous stabilizer can be added to the epoxidation reaction mixture before the organic solvent is directly evaporated off from the epoxidation reaction mixture. Preferably, in the step (3), a phenolic stabilizer and/or a phosphorous stabilizer can be added to the epoxidation reaction mixture in an amount of 0.005 to 5 parts by weight per 100 parts by weight of the finally obtained epoxidized block copolymer before the organic solvent is removed from the epoxidation reaction mixture. Further, preferably, the step (3) can be conducted in such a manner that the epoxidation reaction mixture in the form of a solution or slurry is quantitatively fed into an evaporator; a phenolic stabilizer and/or a phosphorous stabilizer is added to the epoxidation reaction mixture in an amount of 0.005 to 10 parts by weight per 100 parts by weight of the finally obtained epoxidized block copolymer; and the organic solvent is removed from the epoxidation reaction mixture. A preferred epoxidizing agent is an acetic ester solution containing peracetic acid but not containing water.
In the step (3), the epoxidation reaction mixture can be fed into an evaporator to thereby directly evaporate off the organic solvent. The evaporation is conducted by heating. This solvent""s removal preferably involves one or two stages of operation.
The two-stage solvent""s removal can be conducted in such a manner that in the step (3), the epoxidation reaction mixture is fed into an evaporator to thereby evaporate the organic solvent so that the epoxidation reaction mixture is concentrated and the concentrate is fed into a kneading evaporator to thereby remove the organic solvent. In the step (3), each of the evaporator and kneading evaporator can be at a temperature of 80 to 300xc2x0 C. and an internal pressure of not greater than 500 Torr. Preferably, in the step (3), the epoxidation reaction mixture is fed into a thin-film evaporator to thereby evaporate the organic solvent so that the epoxidation reaction mixture is concentrated and the concentrate is fed into a vented twin-screw extruder as one type of kneading evaporator to thereby remove the organic solvent.
The one-stage solvent""s removal can be conducted by, in the step (3), feeding the epoxidation reaction mixture into an evaporator which is preferred to be a vented twin-screw extruder. This vented twin-screw extruder can have such a structure that a heating medium can be passed through the internal part of each screw.
Moreover, the present invention provides an epoxidized block copolymer composition comprising 100 parts by weight of an epoxidized block copolymer (F) obtained by epoxidizing a block copolymer (C) comprising a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound and a polymer block (B) composed mainly of a conjugated diene compound or a hydrogenation product (D) of the block copolymer (C), 0.005 to 10 parts by weight of at least one phenolic and/or phosphorous stabilizer and/or 0.001 to 5 parts by weight of at least one antiblocking agent.
That is, the epoxidized block copolymer (E) or (F) is useful as an additive to adhesives, sealants, coatings and asphalt.
The inventors have made intensive studies and as a result have found that the ratio of hydroxyl groups to epoxy groups of the epoxidized block copolymer exerts a substantial influence on the amount of formed gel. The first embodiment of the present invention has been completed on the basis of this finding.
Illustratively, the first embodiment of the present invention is directed to an epoxidized block copolymer (E) obtained by epoxidizing a block copolymer (C) comprising a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound and a polymer block (B) composed mainly of a conjugated diene compound or a product (D) of hydrogenation of the block copolymer (C), this epoxidized block copolymer (E) having a molar ratio (R) of contained hydroxyl to epoxy ranging from 0.001 to 0.1, this molar ratio (R) being represented by the formula:
R=[hydroxyl]/[epoxy]
wherein [hydroxyl] represents the amount, in terms of the number of moles, of hydroxyl contained per unit weight of the epoxidized block copolymer and [epoxy] represents the amount, in terms of the number of moles, of epoxy contained per unit weight of the epoxidized block copolymer. Further, the first embodiment of the present invention is directed to a process for producing the above epoxidized block copolymer (E) and a composition obtained from the epoxidized block copolymer (E).
In the first embodiment of the present invention, an epoxidized block copolymer is obtained which has a low gel content and is excellent in moldability. This epoxidized block copolymer can most suitably be used in thermoplastic resin and rubbery polymer compositions, coating compositions, sealant compositions, thermosetting compositions, adhesives, asphalt improvers and the like because the amount of formed gel is small especially during the melt kneading while heating.
The term xe2x80x9cblock copolymerxe2x80x9d as used in the first embodiment of the present invention means the block copolymer (C) comprising a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound and a polymer block (B) composed mainly of a conjugated diene compound. The term xe2x80x9cproduct (D) of hydrogenation of the block copolymerxe2x80x9d means a polymer obtained by partially hydrogenating unsaturated carbon bonds contained in the polymer block (B) of the block copolymer through a hydrogenation reaction. The term xe2x80x9cepoxidized block copolymer (E)xe2x80x9d as used in the first embodiment of the present invention means a polymer obtained by epoxidizing unsaturated carbon bonds contained in the polymer block (B) of the block copolymer (C) or product (D) of hydrogenation thereof.
Representative examples of the vinyl aromatic hydrocarbon compounds which can be employed in the formation of the block copolymer (C) include styrene, various alkyl-substituted styrenes such as xcex1-styrenes, alkoxy-substituted styrenes, vinylnaphthalene, alkyl-substituted vinylnaphthalenes, divinylbenzene and vinyltoluene. Of these, styrene is especially preferred. These can be used either individually or in combination.
Representative examples of the conjugated diene compounds which can be employed in the formation of the block copolymer (C) include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene and phenyl-1,3-butadiene. Of these, 1,3-butadiene and isoprene are preferred because these are inexpensive and readily available. The above compounds can be used either individually or in combination.
In the block copolymer (C), the vinyl aromatic hydrocarbon compound and conjugated diene compound which can be employed in the formation thereof are preferably used in a ratio (by weight) of 5/95 to 80/20, still preferably, 10/90 to 60/40. The number average molecular weight of the block copolymer suitable for use in the present invention is preferred to range from 5000 to 500,000, especially, 10,000 to 100,000. When the molecular weight is lower, rubbery elastomer properties are hardly exhibited. On the other hand, when the molecular weight is higher, unfavorably the melting becomes difficult. Herein, the number average molecular weight means the molecular weight determined in terms of standard polystyrene by the use of GPC.
Although the structure of the block copolymer (C) is not particularly limited, it may be, for example, vinyl aromatic hydrocarbon compound/conjugated diene compound block copolymers represented by the formulae: A-B-A, B-A-B and A-B-A-B-A. The structure of the molecule per se thereof may be any of linear, branched and radial configurations or an arbitrary combination of these. In the block copolymer, the vinyl aromatic hydrocarbon compound may be distributed either uniformly or in tapered form. In the copolymer part, the part where the vinyl aromatic hydrocarbon compound is uniformly distributed and/or the part where the vinyl aromatic hydrocarbon compound is distributed in tapered form may be copresent each in plurality.
The process for producing the unepoxidized block copolymer (C) is not particularly limited and any known process can be used. For example, the processes as described in Japanese Patent Publication Nos. 23798/1965, 3252/1972, 2423/1973 and 2892/1981 can be mentioned in which the production is carried out in the presence of, for example, a lithium catalyst in an inert solvent.
The process for producing the block copolymer hydrogenation product (D) is not particularly limited and any known process can be used. For example, the process as described in Japanese Patent Publication Nos. 8074/1967 and 6636/1968 can be mentioned in which the block copolymer (C) is hydrogenated in the presence of a hydrogenation catalyst in an inert solvent. Although the degree of hydrogenation is not particularly limited, when the epoxidation reaction follows, it is required that unsaturated carbon bonds capable of reacting with the epoxidizing agent remain in the molecule of the hydrogenation product (D). This is because the site epoxidized by the epoxidizing agent is the unsaturated bond contained in the polymer block (B).
The process for producing the epoxidized block copolymer (E) according to the first embodiment of the present invention will now be described.
The process according to the first embodiment of the present invention produces an epoxidized block copolymer by subjecting the above-obtained block copolymer (C) or hydrogenation product (D) thereof to the following first to fourth steps.
In the first step according to the first embodiment of the present invention, an organic solvent is added to the block copolymer (C) or product (D) of hydrogenation thereof and mixed together so as to obtain an organic solvent solution having a polymer concentration of 5 to 50% by weight. Representative examples of suitable organic solvents include linear and branched hydrocarbons such as pentane, hexane, heptane and octane and alkyl-substituted derivatives thereof, alicyclic hydrocarbons such as cyclopentane, cyclohexane and cycloheptane and alkyl-substituted derivatives thereof, aromatic hydrocarbons such as benzene, naphthalene, toluene and xylene and alkyl-substituted derivatives thereof, aliphatic carboxylic acid esters such as methyl, ethyl and propyl acetates and halogenated hydrocarbons such as chloroform. Of these, the use of cyclohexane, ethyl acetate, chloroform, toluene, xylene and hexane is preferred from the viewpoint of the solubility of the block copolymer (C) or product (D) of hydrogenation thereof and the easiness of subsequent solvent recovery.
When the concentration of the block copolymer (C) or product (D) of hydrogenation thereof is lower than 5% by weight, actually too much a solvent must be used to an economic disadvantage. On the other hand, when the concentration is higher than 50% by weight, unfavorably the melt viscosity is so high that the mixing of the epoxidizing agent and the organic solvent solution or slurry is unsatisfactory in the second step and that removal of the reaction heat is difficult.
In the second step of the first embodiment of the present invention, unsaturated bonds present in the polymer contained in the organic solvent solution are epoxidized with an epoxidizing agent.
The epoxidation of the block copolymer (C) or product (D) of hydrogenation thereof can be performed by a reaction with the conventional epoxidizing agent.
Examples of epoxidizing agents which can be used in the epoxidation reaction include organic peracids such as peracetic acid, perbenzoic acid, performic acid and trifluoroperacetic acid, hydrogen peroxide and mixtures of hydrogen peroxide, and low molecular fatty acids. Of these, peracetic acid is the most suitable epoxidizing agent because not only is it industrially produced in large quantity so that it can be procured at lowered cost but also its stability is relatively high. It is especially preferred to use peracetic acid in the form of a solution thereof in a solvent such as ethyl acetate. In particular, a peracetic acid/ethyl acetate solution is the most suitable. A catalyst can be used in the epoxidation according to necessity.
Although the amount of added epoxidizing agent is not particularly limited and can be arbitrarily selected depending on, for example, the reactivity of the epoxidizing agent, the desired degree of epoxidation and the amount of unsaturated carbon bonds contained in the employed block copolymer or product of hydrogenation thereof, it is preferred that the amount of epoxidizing agent be determined so that the epoxy equivalent of the finally obtained epoxidized block copolymer (E) range from 140 to 2700.
Still preferably, the epoxy equivalent ranges from 200 to 2000. Herein, the epoxy equivalent is calculated by the formula: epoxy equivalent=1600/{concentration (wt. %) of oxirane oxygen contained in the epoxidized block copolymer} and represents the weight of epoxidized block copolymer per mol of oxirane oxygen.
The concentration of oxirane oxygen is determined by titration using an acetic acid solution of hydrogen bromide. The larger the epoxy equivalent, the lower the concentration of oxirane oxygen. Contrarily, the smaller the epoxy equivalent, the higher the concentration of oxirane oxygen. When the epoxy equivalent is smaller than 140, unfavorably, elastic properties of polymer are hardly exhibited. On the other hand, when the epoxy equivalent is larger than 2700, peculiar properties attributed to the epoxidation are hardly exhibited unfavorably.
The epoxidation reaction temperature is varied depending on, for example, the employed epoxidizing agent, the employed organic solvent and the type and amount of the block copolymer or hydrogenation product thereof and is not particularly limited. For example, when peracetic acid is used as the epoxidizing agent, the reaction temperature preferably ranges from 0 to 70xc2x0 C. When the reaction temperature is lower than 0xc2x0 C., the reaction rate is too low. On the other hand, when the reaction temperature exceeds 70xc2x0 C., unfavorably the formed epoxy ring is opened and decomposition of peracetic acid is promoted. For improving the stability of peracetic acid, a phosphate salt may be added to the reaction system prior to the epoxidation reaction. From the viewpoint of productivity, it is preferred that the epoxidation reaction time be selected within the range of 0.1 to 72 hr, especially, 0.2 to 10 hr.
In the third step of the first embodiment of the present invention, the epoxidation reaction mixture is washed with water and/or neutralized so that the acid value of the reaction mixture does not exceed 5 mgKOH/g. Herein, the acid value is the weight of potassium hydroxide required to neutralize acids contained in 1 g of the crude reaction mixture resulting from the epoxidation reaction, which weight is measured by titration.
The purpose of the water washing and/or neutralization is to remove acids and other by-products incidentally formed by the epoxidation reaction carried out in the preceding step. When the acid value is higher than 5 mgKOH/g, unfavorably, the epoxy ring of the epoxidized block copolymer is opened and the properties of the epoxidized block copolymer are deteriorated.
The water washing may be conducted either continuously or batchwise. In the batchwise washing, it is preferred that washing be repeated a few times with the use of 50 to 1000 parts by weight of water per 100 parts by weight of the crude reaction mixture resulting from the epoxidation. In particular, when a large amount of epoxidizing agent is used, acids are incidentally formed in a large amount corresponding thereto. Thus, it is preferred that, for example, the frequency of washing be increased so as to achieve satisfactory removal of the acids. In the water washing, an inorganic salt such as sodium chloride or sodium sulfate may be added for achieving effective separation of the organic phase from the water phase.
Representative examples of alkaline aqueous solutions which can be used in the above neutralization include aqueous solutions of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, calcium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium acetate and potassium acetate. The above alkali is used in a molar amount required for neutralizing the acids which are present in the reaction mixture. When the amount of alkali is too large, unfavorably the epoxy ring is opened to thereby form hydroxyl. On the other hand, when the amount of alkali is too small, unfavorably acids remain so as to cause deterioration leading to poor properties. For suppressing the opening of epoxy ring caused by exothermic neutralization, it is preferred that the neutralization be conducted while cooling the crude reaction mixture. The neutralization is conducted so that the molar ratio (R) of contained hydroxyl to epoxy ranges from 0.001 to 0.1, preferably, from 0.001 to 0.05.
In the fourth step of the first embodiment of the present invention, the obtained epoxidation reaction mixture containing the epoxidized block copolymer (E) is quantitatively fed by means of, for example, a pump into an evaporator, where the organic solvent is directly evaporated off from the reaction mixture to thereby recover the epoxidized block copolymer. In this step, the content of organic solvent in the epoxidized block copolymer (E) is regulated so as to be not greater than 5000 ppm.
Examples of evaporators which can be used in the first embodiment of the present invention include a flash vessel evaporator, an agitating vessel evaporator, a thin-film evaporator, a wetted wall column evaporator, a longitudinal screwed evaporator and a vented extruder which enable one-stage or at least two stage, i.e., multi-stage concentration. At least two evaporators selected from among the above ones can be used in combination for increasing the production capacity. Of the evaporators, the use of a vented extruder is especially preferred from the viewpoint that the solvent removing capacity is large and that the amount of scorched resin is small.
The vented extruder preferably used in the practice of the first embodiment of the present invention will be described now. The vented extruder is one having at least one, preferably, 1 to 10 and, still preferably, 1 to 5 deairing vent parts. In the extruder, the number of screws is at least one, preferably, at least two. Of these, a vented twin-screw extruder is especially preferred from the viewpoint of the availability for general purposes.
With respect to the vented extruder of the above structure, it is preferred that L/D (L representing the length of screw and D the outer diameter of screw) range from about 2 to 50, especially, from about 4 to 40. It is no matter whether the screws are structured so as to engage with each other or not and whether they are corotating or counterrotating.
A vented twin-screw extruder having such a structure that a heating medium can be passed through the internal part of each screw is the most suitable among the available varieties. The extruder of this structure is preferred from the viewpoint that a large amount of heat taken away at the time of evaporation of the organic solvent can satisfactorily be supplemented by a heat supply. Further, an extruder having a continuous gas phase zone at the upper part of the inside of the extruder is preferred from the viewpoint of the efficiency of removal of the organic solvent.
The internal temperature and internal pressure of the evaporator are determined taking into account, for example, the processing capacity, the properties of polymer (viscosity, thermal stability, etc.), the type and concentration of the organic solvent and the quality of the product. It is preferred that the internal temperature of the evaporator range from 80 to 300xc2x0 C., especially, 120 to 250xc2x0 C. When the internal temperature of the evaporator is lower than 80xc2x0 C., removal of the organic solvent is not satisfactory and so causes low viscosity. On the other hand, when it is higher than 300xc2x0 C., a large amount of gel occurs in the polymer unfavorably. In particular, when the epoxidized block copolymer remains in the evaporator used in the fourth step at high temperatures with the result of occurrence of a large amount of gel, unfavorably not only is the melt viscosity too high but also fisheyes are likely to occur to thereby cause molding defects. The gel content is preferred to be not greater than 5% by weight, especially, not greater than 3% by weight and, still especially, not greater than 1% by weight.
The internal pressure of the evaporator is determined so as to be preferably not greater than 500 Torr, still preferably, within the range of from 1 to 400 Torr. The internal pressure of the evaporator means the pressure at a point exhibiting the lowest pressure in the gas phase zone brought into contact with the resin within the evaporator. With respect to the extruder, generally, the above internal pressure means the value read from a pressure gauge mounted to the vent part. When the internal pressure of the evaporator is higher than 500 Torr, unfavorably, the organic solvent cannot satisfactorily be removed. In the use of the vented extruder, the screw revolution speed ranges from 20 to 500 rpm, preferably, from 30 to 400 rpm.
It is preferred that the organic solvent be directly evaporated off from the epoxidation reaction mixture by the above operation (hereinafter also referred to as the xe2x80x9cdirect solvent removalxe2x80x9d) so that the residual organic solvent content of the finally obtained epoxidized block copolymer is not greater than 5000 ppm, preferably, not greater than 2000 ppm and, still preferably, not greater than 1000 ppm. The organic solvent may involve the one used in the production of the block copolymer (C) or product (D) of hydrogenation thereof, the one used in the epoxidation reaction and the one used in other steps. When the residual organic solvent content is greater than 5000 ppm, unfavorably foaming and odor development are invited in the molding of the epoxidized block copolymer into a product configuration. The residual organic solvent content can easily be regulated by changing the conditions such as the temperature of the evaporator, the internal pressure of the evaporator and the processing speed.
The epoxidized block copolymer having undergone the direct solvent removal by the evaporator can be obtained in the form of any of foamed crumbs, granules and powder and also can be obtained in the form of strands and pellets. Preferably, the epoxidized block copolymer is obtained in the form of pellets.
In the practice of the first embodiment of the present invention, the fourth step can be performed in such a manner that the obtained organic solvent solution of the block copolymer (C) or product (D) of hydrogenation thereof (product obtained upon completion of the above third step) is quantitatively fed by means of, for example, a pump into an evaporator, then a phenolic stabilizer and/or a phosphorous stabilizer is added to the epoxidation reaction mixture and finally the organic solvent is directly evaporated off from the epoxidation reaction mixture. The epoxidized block copolymer (E) obtained in the above manner exhibits a markedly improved thermal stability, has a less tendency for gelation even if allowed to stand still at high temperature and enables marked suppression of a hue deterioration. Moreover, for adding a stabilizer to a plastic or rubber, it is generally needed to knead the stabilizer into the copolymer by the use of a device such as a kneading extruder. However, in the above method according to the first embodiment of the present invention, it is only needed to put the stabilizer in the epoxidation reaction mixture containing the epoxidized block copolymer (E) and thus it is not needed to conduct kneading of the stabilizer. This ensures operational and economic advantages.
Representative examples of phenolic stabilizers which can be used in the first embodiment of the present invention include tetrakis(methylene-3-(3xe2x80x2,5xe2x80x2-di-tert-butyl-4xe2x80x2-hydroxyphenyl)propionate)methane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4xe2x80x2-hydroxybenzyl)benzene, 2,6-di-tert-butyl-4-methylphenol, 4-hydroxymethyl-2,6-di-tert-butylphenol, 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, triethylene glycol bis(3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)-propionate), 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid, 2,2xe2x80x2-methylenebis(4-methyl-6-tert-butylphenol), 3,9-bis(2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, 2,6-di-tert-butyl-4-ethylphenol, butylated hydroxyanisole, 2,2xe2x80x2-dihydroxy-3,3xe2x80x2-dicyclohexyl-5,5xe2x80x2-dimethyldiphenylmethane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4xe2x80x2-butylidene-bis(6-tert-butyl-m-cresol), bis(3-cyclohexyl-2-hydroxy-5-methylphenyl)-methane, 2,2xe2x80x2-methylenebis(4-ethyl-6-tert-butylphenol) and 1,1-methylenebis(2xe2x80x2-methyl-4xe2x80x2-hydroxy-5xe2x80x2-tert-butylphenyl)butane. These phenolic stabilizers can be used in combination.
Representative examples of phosphorous stabilizers which can be used in the first embodiment of the present invention include trisnonylphenyl phosphite, tris(2,5-di-tert-butylphenyl)phosphite, tris(2-di-tert-butylphenyl)phosphite and tris(2,4-bis(1,1-dimethylpropyl)phenyl)phosphite. These phosphorous stabilizers can be used in combination.
In the first embodiment of the present invention, the phenolic stabilizer and the phosphorous stabilizer may be used each independently or in combination. The phenolic stabilizer and/or phosphorous stabilizer is added in an amount of 0.005 to 10 parts by weight, preferably, 0.05 to 3 parts by weight and, still preferably, 0.1 to 2 parts by weight in terms of the amount of each of the stabilizers per 100 parts by weight of epoxidized block copolymer finally obtained after the removal of the solvent. The amount of stabilizer to be added can be easily calculated from the concentration of block copolymer in the solution and from the desired concentration. When the amount of added stabilizer is smaller than 0.005 part by weight, the thermal stability would be deteriorated. On the other hand, even when the amount is greater than 10 parts by weight, further thermal stability improving effect is trivial. Therefore, the use of stabilizer in such a large amount is not desired from the economic point of view.
In the practice of the first embodiment of the present invention, the fourth step can comprise removing the organic solvent from the above produced organic solvent solution of block copolymer (C) or product (D) of hydrogenation thereof (product obtained upon completion of the above third step) by means of a first evaporator (first-stage concentration) and then evaporating off the remaining volatile component by means of a second evaporator of the kneading type (second-stage concentration), so that the organic solvent can be evaporated off under condition such that the time of residence of polymer is short, i.e., the polymer having a residual organic solvent concentration of not greater than 500 ppm can be produced without suffering from long heat history.
Examples of evaporators which can be used in the first-stage concentration of this step (first evaporators) include a shell and tube evaporator, a liquid film evaporator, a centrifugal thin-film evaporator and a plate evaporator of these, a shell and tube evaporator, a centrifugal thin-film evaporator and a plate evaporator are preferred. These have a large surface brought into contact with the epoxidation reaction mixture and are suitable for use in the concentration conducted at a high solvent content. The first-stage concentration is conducted so that the organic solvent content (volatile component content) ranges from 5 to 70% by weight, preferably, from 20 to 30% by weight. The use of the first evaporator enables reducing the size of the second evaporator.
Examples of kneading evaporators which can be used in the second-stage concentration (second evaporators) include a twin-screw evaporator of the surface renewing, self-cleaning type and a vented extruder each having kneading shafts. For realizing a large heating surface area, it is preferred to employ a kneading evaporator in which a heating medium can be passed through the internal part of each screw. The kneading evaporator with this structure can satisfactorily supply a large amount of heat required for evaporating the organic solvent. Further, this kneading evaporator is especially preferred from the viewpoint that the piston flow properties free of back mixing are exhibited to thereby ensure excellent blending performance and that the evaporation surface area can be large. With respect to the structure of the kneading evaporator, it is preferred that L/D (L representing the length of screw and D the outer diameter of screw) range from about 2 to 50, especially, from about 4 to 40. It is no matter whether the screws are structured so as to engage with each other or not and whether they are corotating or counterrotating. The kneading evaporator enables removing the organic solvent without detriment to the stability of the epoxidation product even from the epoxidation reaction mixture whose viscosity has increased because of the reduction in the organic solvent content.
Oil and other heating media, steam and electrical heater can be used as the heating source for each evaporator.
In a practical embodiment of this method, first, the epoxidation reaction mixture is continuously fed by means of a gear pump into the first evaporator, in which the solvent is distilled off within a flash tank at heating temperature not lower than the boiling point of the solvent. The epoxidation reaction mixture may be one washed with water in advance. The water washing may be conducted either continuously or batchwise. In the batchwise washing, it is preferred that washing be repeated a few times with the use of 50 to 1000 parts by weight of water per 100 parts by weight of the crude reaction mixture resulting from the epoxidation.
The organic solvent contained in large quantity in the epoxidation reaction mixture can easily be removed by conducting heating evaporation in the first evaporator.
In this method, the volatile component is distilled off from the concentrate obtained by evaporation by means of the first evaporator with the use of the second evaporator to thereby separate the epoxidized block copolymer from the organic solvent. Distilling off the volatile component with the use of the second evaporator enables stably evaporating the organic solvent remaining in the concentrate under condition such that the time of residence of concentrate is short, i.e., the epoxidized block copolymer can be produced without suffering from long heat history.
The obtained epoxidized block copolymer can be extrusion molded in the customary manner into any form selected from among those of strands, pellets, foamed crumbs, granules and powder, preferably, into the form of pellets.
The internal temperature and internal pressure of each of the evaporator and the kneading evaporator are determined taking into account, for example, the processing capacity, the properties of polymer (viscosity, thermal stability, etc.), the type and concentration of the solvent and the quality of the product. It is preferred that the internal temperature of each of both the evaporators range from 80 to 300xc2x0 C., especially, 120 to 250xc2x0 C. When the internal temperature of the evaporator is lower than 80xc2x0 C., the viscosity is increased with the result that removal of the organic solvent becomes difficult unless the degree of pressure reduction is raised. On the other hand, when it is higher than 300xc2x0 C., unfavorably gelation occurs in the polymer. In particular, when the epoxidized block copolymer remains in the evaporator with the result of occurrence of a large amount of gel, unfavorably not only is the melt viscosity too high but also fisheyes are likely to occur in the product to thereby cause molding defects. The gel content is preferred to be not greater than 5% by weight, especially, not greater than 3% by weight and, still especially, not greater than 1% by weight. The gel content is expressed as the weight percentage of insolubles in tetrahydrofuran (THF).
The first embodiment of the present invention is characterized in that the epoxidized block copolymer (E) obtained by the above method has a molar ratio (R) of contained hydroxyl to epoxy ranging from 0.001 to 0.1, this molar ratio (R) being represented by the formula:
R=[OH]/[epoxy]
wherein [OH] represents the amount, in terms of the number of moles, of hydroxyl contained per unit weight of the epoxidized block copolymer and [epoxy] represents the amount, in terms of the number of moles, of epoxy contained per unit weight of the epoxidized block copolymer.
The hydroxyl is mainly formed by the opening of epoxy ring by the action of, for example, an acid or a base. The ratio R preferably ranges from 0.001 to 0.05. When the ratio R is greater than 0.1, unfavorably gelation is likely to occur in the polymer.
It has been found that the following measures are effective in controlling so that the ratio R of hydroxyl to epoxy is low as above. (1) Peracetic acid is used as the epoxidizing agent so the reaction is effected under mild temperature condition. (2) A peracetic acid/ethyl acetate epoxidizing agent is used to thereby enable suppressing the epoxy ring opening reaction (formation of hydroxyester group, etc.) more effectively than in the use of epoxidizing agents containing a strong acid such as sulfuric acid or p-toluenesulfonic acid and/or water, so that the value R becomes small. (3) Acetic acid is removed by washing with water and neutralization to thereby enable suppressing the epoxy ring opening at high temperatures during the removal of solvent, so that the value R becomes small.
The acid value of the epoxidized block copolymer is preferred to be not greater than 10 mgKOH/g. Herein, the acid value of the epoxidized block copolymer is the weight of potassium hydroxide required to neutralize acids contained in 1 g of the epoxidized block copolymer obtained through epoxidation reaction, solvent removal and drying, which weight is measured by titration. The acids are mainly formed as by-products in the epoxidation reaction. For example, when peracetic acid is used as the epoxidizing agent, acetic acid is formed as by-product in the epoxidation reaction. Further, acids attributed to starting material impurities and to various additives used in the above production of epoxidized block copolymer are also included in the acid value referred to in the first embodiment of the present invention as long as the amount thereof is determined by titration with potassium hydroxide. When the acid value is higher than 10 mgKOH/g, the gel content of finally obtained epoxidized block copolymer is so high that the melt flow processability is deteriorated unfavorably. In particular, when the acid value is too high in the melt kneading of the epoxidized block copolymer together with other resin or rubber at high temperatures, a large amount of gel is formed during the melt kneading, so that the moldability of the composition is gravely deteriorated.
It is preferred that the chloride ion content of the epoxidized block copolymer be not greater than 7 ppm. One of the measures for lowering the chloride ion content of the epoxidized block copolymer is to use a peracetic acid epoxidizing agent containing no chloride ion as the epoxidizing agent.
The epoxidized block copolymer according to the first embodiment of the present invention can be obtained in the form of any of liquid, foamed crumbs, strands, pellets and powder. Preferably, the epoxidized block copolymer is obtained in the form of pellets.
According to necessity, the epoxidized block copolymer according to the first embodiment of the present invention can be blended with various additives, e.g., a thermal stabilizer, an age resister, a crosslinking agent, an ultraviolet absorber, an inorganic filler such as silica, talc, carbon or glass fiber, an organic filler, a plasticizer and a softening agent such as oil before use thereof. The time of addition is not particularly limited and the additives can be incorporated at any time before finally obtaining the epoxidized block copolymer.
In the first embodiment of the present invention, an antiblocking agent can be added in an amount of 0.001 to 5 parts by weight, preferably, 0.01 to 2 parts by weight and, still preferably, 0.05 to 1 part by weight per 100 parts by weight of the epoxidized block copolymer (E) for inhibiting mutual blocking of the epoxidized block copolymer (E) according to the first embodiment of the present invention. When the amount of added antiblocking agent is less than 0.001 part by weight, unfavorably, satisfactory antiblocking effect cannot be exerted. On the other hand, when the amount is greater than 5 parts by weight, also unfavorably, the inherent properties of the epoxidized block copolymer, especially, the transparency thereof is gravely deteriorated although the blocking can be avoided. Mutual blocking of the obtained epoxidized block copolymer composition is substantially inhibited not only in the composition per se of powdery or pelletized form but also in various products of film or sheet form prepared therefrom.
Examples of suitable antiblocking agents include silicon compounds, fatty acid salts, fatty acid esters, fatty acid amides and nonionic surfactants. Representative examples of the silicon compounds include silicon oxide, silicone oil, silicone emulsion and other silicone fluids. The silicone fluids include alkyl, aryl and cycloalkyl-substituted silicone compounds having 0 to 12 carbon atoms per unit. Of these, silicon oxide and polydimethylsiloxane are especially preferred. It is preferred that silicon oxide have an average particle size ranging from 0.005 to 25 xcexcm.
In the fatty acid residue employed to constitute a fatty acid salt or fatty acid ester as the antiblocking agent, the number of carbon atoms per molecule is selected within the range of 10 to 20, preferably, 12 to 18. When the number of carbon atoms is less than 10 or greater than 20, unfavorably, satisfactory antiblocking effect cannot be exerted. Representative examples of the fatty acid salts include salts composed of metals belonging to Groups I, II, III and IV of the periodic table and acids such as lauric acid, myristic acid, palmitic acid, stearic acid and oleic acid. Of these, calcium stearate is especially preferred. Representative examples of the fatty acid esters include glycerol monostearate, glycerol distearate and glycerol tristearate. Glycerol monostearate is especially preferred. Both the fatty acid salts and fatty acid esters may be used either individually or in combination.
Representative examples of the fatty acid amides as the antiblocking agents include stearamide, oleamide and ethylenebisstearamide. Representative examples of the noionic surfactants as the antiblocking agents include sorbitan esters, propylene glycol fatty acid esters, sucrose fatty acid esters, citric acid mono(di or tri)stearates, pentaerythritol fatty acid esters, trimethylol fatty acid esters, polyglycerol fatty acid esters, polyoxyethylene glycerol fatty acid esters, polyesters, polyoxyethylene sorbitan fatty acid esters, polyethylene glycol fatty acid esters, polypropylene glycol fatty acid esters, polyoxyethylene glycol aliphatic alcohol ethers, polyoxyethylene alkylphenyl ethers, N,N-bis(2-hydroxyethylene) fatty amines, fatty acid/diethanolamine condensates, polyoxyethylene/polyoxypropylene block polymers, polyethylene glycol and polypropylene glycol. Especially preferred nonionic surfactants are those having polyoxyethylene units, such as polyoxyethylene glycerol fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene aliphatic alcohol ethers, polyoxyethylene alkylphenyl ethers and polyoxyethylene/polyoxypropylene block polymers.
At least one member may be selected from each of the above antiblocking agent groups or, occasionally, at least two members may be selected therefrom and used in mixture. Also, members may be selected from a plurality of groups selected from the various antiblocking agent groups consisting of the silicon compound, fatty acid salt, fatty acid ester, fatty acid amide and nonionic surfactant groups and used in mixture.
With respect to the method of incorporating the antiblocking agent, it is preferred that the antiblocking agent be deposited on the surfaces of pellets of the epoxidized block copolymer (E) from the economic point of view. Examples of the methods include (1) the method in which the pellets are directly covered with the antiblocking agent, or the pellets are coated with the antiblocking agent and, according to necessity, dried; (2) the method in which the strand extruded through an extruder die is cut in water in which the antiblocking agent has been dissolved or suspended in advance and the obtained wet pellets are dried to thereby deposit the antiblocking agent on the pellet surface; and (3) the method in which the polymer (E) and the antiblocking agent are dryblended, and kneaded and pelletized by the use of a general-purpose extruder.
The epoxidized block copolymer according to the first embodiment of the present invention can also be used in the form of a thermoplastic resin composition containing a thermoplastic resin and/or rubbery polymer. The thermoplastic resin composition according to the first embodiment of the present invention comprises 99 to 1% by weight of the epoxidized block copolymer (a) and 1 to 99% by weight of the thermoplastic resin and/or rubbery polymer (b).
The thermoplastic resin as the component (b) used in the first embodiment of the present invention generally refers to the resin which is melted by heating and moldable into any desired configuration. Examples of the thermoplastic resins include polyolefin resins such as polyethylene and polypropylene; polyamide resins such as nylon 46, nylon 6 and nylon 66; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; crystalline thermoplastic polymers such as polyamide elastomers and polyester elastomers; rubber-modified polymers such as ABS, AES, AAS and MBS resins; noncrystalline thermoplastic polymers such as acrylonitrile/styrene copolymer, styrene/methyl methacrylate copolymer, polystyrene, polymethyl methacrylate, polycarbonate and polyphenylene oxide; graft polymers comprising polymer units whose main repeating structural units are composed of an xcex1-monoolefin having 2 to 8 carbon atoms, the polymer units being grafted with another polymer, such as graft polymer comprising ethylene/propylene copolymer grafted with acrylonitrile/styrene copolymer, graft polymer comprising ethylene/butene copolymer grafted with acrylonitrile/styrene copolymer, graft polymer comprising ethylene/butene copolymer grafted with butyl acrylate/methyl methacrylate copolymer and graft polymer comprising ethylene/butene copolymer grafted with methyl methacrylate copolymer. The polyamide resins, polyester resins and polycarbonate are especially preferred as a component capable of improving the heat resistance of the composition.
The rubbery polymer as another component constituting the above component (b) generally refers to natural and synthetic rubbers. Representative examples of the rubbery polymers include styrene/butadiene rubber and product of hydrogenation thereof; isoprene rubber, nitrile rubber and products of hydrogenation thereof; and chloroprene rubber, butyl rubber, ethylene/propylene rubber, ethylene/propylene/diene rubber, ethylene/butene rubber, ethylene/butene/diene rubber, acrylic rubber, xcex1,xcex2-unsaturated nitrile/acrylic ester/conjugated diene terpolymer rubber, chlorinated polyethylene rubber, fluororubber, silicone rubber, urethane rubber, epichlorohydrin rubber, polysulfide rubber, styrene/butadiene block polymer and products of hydrogenation thereof.
Of these, preferred rubbery polymers are rubbers whose degree of saturation or unsaturation is essentially low, such as product of hydrogenation of styrene/butadiene rubber; products of hydrogenation of ethylene/propylene rubber, ethylene/propylene/diene rubber, ethylene/butene rubber, ethylene/butene/diene rubber, acrylic rubber, chlorinated polyethylene rubber, fluororubber, silicone rubber, urethane rubber, epichlorohydrin rubber, polysulfide rubber and styrene/butadiene block polymer; and xcex1,xcex2-unsaturated nitrile/acrylic ester/conjugated diene terpolymer rubber, and are modified rubbers comprising these and, bonded therewith, functional groups.
The thermoplastic resin composition or elastomer composition according to the first embodiment of the present invention comprises the epoxidized block copolymer (a) and the thermoplastic resin and/or rubbery polymer (b) as main components. In the composition, the component (a) is blended in an amount of 99 to 1% by weight, preferably, 95 to 5% by weight and, still preferably, 90 to 10% by weight and the component (b) is blended in an amount of 1 to 99% by weight, preferably, 5 to 95% by weight and, still preferably, 10 to 90% by weight.
When the amount of the component (a) exceeds 99% by weight, the property improving effect is unsatisfactory. On the other hand, when it is less than 1% by weight, the various properties as the elastomer are deteriorated unfavorably. When the amount of the component (b) is less than 1% by weight, the property improving effect of the addition of the component (b) is not recognized. On the other hand, when it exceeds 99% by weight, the characteristics of the thermoplastic elastomer are lost unfavorably.
A very wide range of components (b) are used in the first embodiment of the present invention. This is because the epoxidized block copolymer as the component (a) widely changes from a rubbery very flexible form to a hard resin form.
Therefore, whether to employ the thermoplastic resin, the rubbery polymer or a mixture thereof as the component (b) depends mainly on the properties of the component (a) and the purpose of the composition to be obtained.
Specifically, generally, when the vinyl aromatic compound content of the component (a) is not greater than 40% by weight, the component (a) has rubbery flexible properties. Thus, it is desired to design so that the thermoplastic resin is blended as the component (b) to thereby obtain a well balanced thermoplastic polymer composition.
On the other hand, when the vinyl aromatic compound content of the component (a) is greater than 60% by weight, the component (a) exhibits rather resinous properties. Thus, it is desired to design the composition as a thermoplastic elastomer by adding the rubbery polymer as the component (b). When the vinyl aromatic compound content of the component (a) is greater than 40% by weight but less than 60% by weight, it is desired to design the composition as a well balanced thermoplastic elastomer as a whole by simultaneously employing the thermoplastic resin and the rubbery polymer as the component (b).
Moreover, in the first embodiment of the present invention, a composition design can be made taking advantage of an inherent property of the epoxidized block copolymer as the component (a), i.e., the property of acting as a compatibilizer between polymers different from each other. In the use of the block polymer as a compatibilizer, the amount of added block polymer is generally known to be satisfactory if it is about a few percents by weight. The minimum usage of the component (a) of the present invention of about 1% by weight results from taking into consideration the use of the component (a) as a compatibilizer.
That is, in the use of the component (a) as a compatibilizer, joint use is made of the thermoplastic resin and rubbery polymer as the component (b) and, for example, a thermosetting resin as a component (c).
Combinations of specified thermoplastic resins and specified rubbery polymers can be mentioned as enabling an effective action of the component (a) as the compatibilizer.
Examples of such specified thermoplastic resins include styrene resins (such as polystyrene, AS resin, ABS resin, AAS resin, AES resin, ACS resin, MBS resin, HIPS resin and styrene/butadiene copolymer), aromatic polyethers (such as polyphenylene ether), polycarbonate resin, polyolefin resins such as polyethylene, polypropylene and polybutene-1, graft polymers comprising a polymer composed mainly of an xcex1-monoolefin having 2 to 8 carbon atoms grafted with another polymer and mixtures thereof.
Examples of the above rubbery polymers include monoolefinic copolymer rubbers such as ethylene/propylene rubber, ethylene/propylene/diene rubber, ethylene/butene rubber and ethylene/butene/diene rubber, chlorinated polyethylene rubber, product of hydrogenation of styrene/butadiene rubber, product of hydrogenation of nitrile rubber and product of hydrogenation of styrene/butadiene block polymer. The above combination of thermoplastic resin and rubbery polymer is a combination of polymers having a polystyrene structure which is the fundamental structure of the epoxidized block copolymer according to the first embodiment of the present invention, a structure similar to the polyolefin structure and a structure which has affinity with the aromatic vinyl polymer. However, the epoxidized block copolymer according to the first embodiment of the present invention has epoxy groups, so that it acts as a compatibilizer with polymers having generally been incompatible therewith through the affinity and chemical reaction between functional groups. Examples of the thermoplastic resins having the affinity and reactivity with epoxy, with which the epoxidized block copolymer of the present invention effectively acts as the compatibilizer (the term xe2x80x9chaving the affinity and reactivity with epoxyxe2x80x9d used herein means the presence in the resin of residue (e.g., carboxyl, hydroxyl or amino residue) or bond (e.g., ester bond or amide bond)) include polyamide resins such as nylon 6, nylon 66, nylon 46, nylon 11 and nylon 12, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate, polyimides, polyamideimides, carboxylated polyolefins (such as ethylene/(meth)acrylic acid copolymer and polypropylene modified with maleic acid), polyvinyl acetate, ethylene/vinyl acetate copolymer and mixtures thereof.
Further, examples of the rubbery polymers reactive with epoxy capable of effectively acting as the compatibilizer include polyamide elastomers, polyester elastomers, epichlorohydrin rubber and urethane rubber.
Even when the component (a) is used as the compatibilizer, other thermoplastic resin and/or rubbery polymer than mentioned above can be blended in the composition.
Moreover, for example, phenol, epoxy, melamine, unsaturated polyester and alkyd resins may be blended as the component (c) in the composition.
With respect to the above particulars of the combination of the components (a) and (b), a generalized description has been given of the relationship between the properties of the component (a) and the polymer used as the component (b). The composition of the present invention is not limited to the above particulars and the particular of component (b) can be selected according to the purpose.
The polymer used as the component (b) may be composed of a mixture of a plurality of thermoplastic resins and/or a plurality of rubbery polymers.
When the thermoplastic resin and the rubbery polymer are to be used in combination as the component (b), they can be used in arbitrary proportions according to the desired performance of the final composition.
The above thermoplastic polymer composition comprising the components (a) and (b) according to the first embodiment of the present invention can be kneaded by the use of conventional kneading apparatus such as rubber mill, Brabender mixer, Banbury mixer, pressure kneader and twin-screw extruder. These may be of hermetically closed or open type but those which can be flashed with inert gas are preferred.
The kneading is conducted at a temperature at which all the blended components are melted, which temperature is generally preferred to range from 140 to 300xc2x0 C., especially, from 160 to 280xc2x0 C. In the kneading, all the components may simultaneously be kneaded together or the multistage division kneading method may be adopted in which any arbitrary component are kneaded and remaining components are added, followed by further kneading.
The thermoplastic resin composition of the first embodiment of the present invention can be blended with various additives, e.g., an age resister, a crosslinking agent, a thermal stabilizer, an ultraviolet absorber, an inorganic filler such as silica, talc, carbon or glass fiber, a plasticizer and a softening agent such as oil according to necessity before use thereof.
Moreover, the epoxidized block copolymer according to the first embodiment of the present invention can be used in the form of a thermosetting resin composition. Examples of the thermosetting resins which can be blended with the epoxidized block copolymer employed in the first embodiment of the present invention include a phenolic resin, an epoxy resin, a melamine resin, an unsaturated polyester resin and an alkyd resin. Of these, the phenolic resin, epoxy resin and unsaturated polyester resin are preferred from the viewpoint that the blending can be easily made.
Although the blending proportion of the epoxidized block copolymer to the thermosetting resin is varied according to the purpose, the content of epoxidized block copolymer in the composition ranges from 1 to 80% by weight, preferably, from 1 to 50% by weight and, still preferably, from 2 to 25% by weight.
When the content of epoxidized block copolymer is less than 1% by weight, the impact resistance improving effect is poor. On the other hand, when it exceeds 80% by weight, the high strength which is the inherent feature of the thermosetting resin cannot be maintained.
Although the method of blending the thermosetting resin composition according to the first embodiment of the present invention is not particularly limited, it is preferred that the composition be heated and kneaded. Use can be made of a hermetically closed mixer such as Banbury mixer, a roll mill or an extruder.
The thermosetting resin composition of the first embodiment of the present invention can be blended with various additives, e.g., an age resister, a stabilizer, a plasticizer, a softening agent, inorganic and organic fillers, a reinforcement and a curing agent according to necessity before use thereof.
Curing agents commonly used in the curing of epoxy resins can be employed as the curing agent in the first embodiment of the present invention. Examples thereof include amines, polyamide resins, acid anhydrides, polymercaptan resins, novolak resins, dicyandiamide and amine complex of boron trifluoride. Examples of the amines include aliphatic polyamines such as diethylenetriamine, triethylenetetramine, menthenediamine, m-xylylenediamine and bis(4-amino-3-methylcyclohexyl)methane; adducts obtained by the reaction thereof with conventional epoxy compounds and products obtained by reacting the aliphatic polyamines with any of acrylonitrile and ketones; aromatic polyamines such as m-phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone and diaminodiphenyl sulfide; adducts obtained by the reaction of the aromatic polyamines with conventional epoxy compounds; secondary and tertiary amines such as tris(dimethylaminomethyl)phenol, piperidine, imidazole and derivatives thereof and their salts; and mixtures of the above amines.
Examples of the polyamide resins include products obtained by reacting fatty acids including dimer and trimer acids with aliphatic polyamines.
Examples of the acid anhydrides include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnudic anhydride, succinic anhydride, dodecenylsuccinic anhydride, and mixtures thereof.
Examples of the novolak resins include resinous low-molecular-weight products obtained by formaldehyde condensation with phenol or a mixture of phenol, cresol and dihydroxybenzene.
Examples of the amine complexes of boron trifluoride include complexes of boron trifluoride with low-molecular-weight amine compounds such as monoethylamine, piperidine, aniline, butylamine, dibutylamine, cyclohexylamine, dicyclohexylamine, tributylamine and triethanolamine.
Also, use can be made of other curing agents, e.g., salts such as diazonium, iodonium, bromonium and sulfinium salts of superstrong acids such as boron tetrafluoride, phosphorus hexafluoride and arsenic hexafluoride.
The epoxidized block copolymer obtained by the process according to the first embodiment of the present invention can be utilized not only as various molded items such as a sheet, a film, variously shaped injection moldings and a hollow shaped article but also as a modifier of various thermoplastic resins, a pressure sensitive adhesive, a raw material of adhesives, an asphalt modifier and raw materials of household electric appliances, automobile parts, industrial parts, household goods and toys.
Of the above usages, the epoxidized block. copolymer according to the first embodiment of the present invention is especially useful as adhesives (including a pressure sensitive adhesive, a contact adhesive, a laminating adhesive and an assembly adhesive), a sealant, a coating, an asphalt improver, a film and a printing plate. Still especially, the epoxidized block copolymer of the present invention can suitably be used in an adhesive composition, a sealant composition, a coating composition and an asphalt composition.
Each of the various compositions according to the first embodiment of the present invention is loaded with not only the epoxidized block copolymer and the curing auxiliary or curing agent (described above) but also with various combinations of components including an adhesion promoter or tackifier, a plasticizer, a filler, a solvent, a stabilizer and other components (e.g., asphalt) so as to conform to the performance required for each individual use.
Examples of general tackifiers are a diene/olefin copolymer prepared from piperidine and 2-methyl-2-butene and an aliphatic hydrocarbon resin prepared from 1,3-pentadiene.
Also, an aromatic resin can be used as the tackifier if it is blendable with specified polymers used in the composition. Generally, although use can be made of a mixture of an aromatic resin with a high softening point and an aromatic resin with a low softening point, these resins should simultaneously have ring-and-ball softening points of 80 to 118xc2x0 C. Examples of the suitable resins include coumarone/indene resin, polystyrene resin, vinyltoluene/xcex1-methylstyrene copolymer and polyindene resin.
Other tackifiers similarly suitable for use in the composition according to the first embodiment of the present invention are, for example, hydrogenated rosin, rosin ester, polyterpene, terpene phenol resin and polymerized mixed olefin, low-softening-point resin and liquid resin. An example of the liquid resin is resin Adtac LV (Adtac being trademark) produced by Hercules. The tackifier is selected from among saturated resins, hydrogenated dicyclopentadiene resin, hydrogenated polystyrene and poly-xcex1-methylstyrene for attaining excellent thermal oxidation resistance and color stability. The tackifier is used in an amount of 0 to 400 parts by weight, preferably, 20 to 350 parts by weight and, optimally, 20 to 150 parts by weight per 100 parts by weight of the epoxidized block copolymer. A specified tackifier is selected mainly on the basis of specified polymer used in the relevant adhesive composition.
The composition according to the first embodiment of the present invention can contain a plasticizer such as a rubber extender plasticizer, a compounding oil, an organic or inorganic pigment and a dye. The compounding oil is well known by experts and includes both an oil of high saturation content and an oil of high aromatic content. Suitable plasticizers are high-saturation oil (e.g., Tufflo 6056 and 6204 oils (Tufflo being trademark) produced by Arco) and processing oil (e.g., Shellflex 371 (Shellflex being trademark) produced by Shell). Also, use may be made of plasticizers such as phthalic esters, aliphatic dibasic acid esters and phosphoric esters in the composition according to the first embodiment of the present invention, the rubber compounding oil is used in an amount of 0 to 500 parts by weight, preferably, 0 to 100 parts by weight and, optimally, 0 to 60 parts by weight per 100 parts by weight of the epoxidized block copolymer.
Various fillers and pigments can be blended in coating and sealant compounds. As examples thereof, in particular, exterior coatings and sealants can be mentioned to which fillers are added for not only exerting desired effects but also improving coating and sealant properties such as weather resistance. Various fillers can be used, examples of which include calcium carbonate, clay, talc, silica, glass fiber, zinc oxide and titanium dioxide. The amount of filler generally ranges from 0 to 65% by weight based on the weight of nonsolvent components of the compound, depending on the type of filler used and the intended use of coating or sealant. Especially suitable filler is titanium dioxide.
In the application of the coating or sealant in the form of a solution in a solvent, the organic components of the compound are dissolved in a solvent or solvent blend. An aromatic hydrocarbon solvent (e.g., toluene, xylene or Shell Cyclo Sol 53) is suitable. Also, use can be made of aliphatic hydrocarbon solvents such as hexane, naphtha and mineral spirit. According to necessity, use may be made of a solvent blend consisting of a hydrocarbon solvent and a polar solvent. Examples of suitable polar solvents include esters (e.g., isopropyl acetate), ketones (e.g., methyl isobutyl ketone) and alcohols (e.g., isopropyl alcohol). The amount of polar solvent used depends on the structures of selected specified polar solvent and specified polymer which is used in the compound. Generally, the amount of polar solvent used ranges from 0 to 50% by weight based on the weight of solvent blend.
An antioxidant may be added to the composition for protecting the product from deterioration attributed to oxidation during the production and use of the composition. A combination of a primary antioxidant and a secondary antioxidant is suitable. This combination is, for example, a combination of a sterically hindered phenol derivative and a phosphite or thioether, e.g., a combination of hydroxyphenyl propionate and an aryl phosphate or thioether or a combination of aminophenol and an aryl phosphate. Examples of advantageous antioxidant combinations include a combination of 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane (Irganox 1010 (Irganox being trademark) produced by Ciba-Geigy) and tris(nonylphenyl)phosphite (Polygard HR (Polygard being trademark) produced by Uniroyal) and a combination of Irganox 1010 and bis(2,4-di-t-butyl)pentaerythritol diphosphite (Ultranox 626 (Ultranox being trademark) produced by Borg-Warner).
All the adhesive, coating and sealant compositions based on the epoxidized block copolymer according to the first embodiment of the present invention comprises specified combinations of various compound components disclosed herein. What components are to be used is not particularly limited. Specified types of components can be selected and their concentrations can be regulated so that the composition is securely provided with a combination of required properties in accordance with arbitrary usage of the specified adhesive, coating and sealant. In the above composition, it is preferred that the content of the epoxidized block copolymer be at least 5% by weight.
The two necessarily used components of each of the adhesive, coating and sealant are the epoxidized block copolymer and the curing agent. The curing agent can be selected from among the above large number of varieties. In addition to these two components, whether or not to use various resins, fillers, pigments, plasticizers, reactive oligomers, stabilizers and/or solvents can be determined.
The coating is mostly a thin nonsticky pigment-filled composition applied to a support for protecting or decorating the support. Therefore, it may be required to use an epoxidized block copolymer hydrogenated so as to impart a satisfactory durability. Selection of the resin is made so as to ensure the maximum durability and the minimum dust collection. Selection of the filler and pigment is carefully made so as to impart the optimal durability and color. The coating mostly contains a solvent in relatively high concentration so that the application is facilitated and a smooth dry coating is provided.
The sealant is an agent which fills gaps. Therefore, it is used in a relatively thick layer so that the spacing between two supports is filled. As the two supports often make relative move, the sealant is generally a low-modulus composition which enables taking this move into consideration. As the sealant is often exposed to the open air, usually, use is made of the hydrogenated epoxidized block copolymer. The resin and plasticizer are selected so as to minimize the dust collection while maintaining the low modulus. The filler and pigment are selected so as to provide suitable durability and color. The sealant is applied in a relatively thick layer, so that the solvent concentration is rendered as low as possible for minimizing the shrinkage.
The adhesive, coating and sealant compositions according to the first embodiment of the present invention can be produced by blending the components at high temperature (preferably, 50 to 200xc2x0 C.) until a uniform blend is obtained (generally, less than 3 hr). Various blending methods are known in the art, any of which can be employed as long as a uniform blend is formed. The obtained composition can be used in various applications. Alternatively, the components may be blended into a solvent.
The adhesive composition according to the first embodiment of the present invention can be used as a large variety of adhesives, e.g., a laminating adhesive, a pressure sensitive adhesive, a bonding adhesive, a hot melt adhesive, a solvent type adhesive and an aqueous adhesive from which water is removed before curing. Although each adhesive may consist only of the epoxidized block copolymer, generally, it is composed of a compounded composition comprising the epoxidized-block copolymer as an active ingredient and other commonly known adhesive composition components. When the hot melt is applied at 100xc2x0 C. or higher temperatures, the effect of the presence of water and other low-molecular-weight cationic polymerization inhibitor can be minimized. Therefore, the optimum hot melt application is conducted at about 100xc2x0 C. or higher temperatures. The heating of the adhesive before the curing and after the curing can further promote the curing or postcuring.
The composition according to the first embodiment of the present invention is suitably used in the production of a pressure sensitive adhesive tape and label. This pressure sensitive adhesive tape consists of a soft packing sheet and, applied to one main surface thereof, a layer of the adhesive composition of the present invention. The packing sheet can be composed of a plastic film, paper or any other appropriate material. The above tape can include other various layers or coatings commonly used in the production of pressure sensitive adhesive tapes (e.g., primer, release coating and the like). When no tackifier is added, the composition according to the first embodiment of the present invention is used as the adhesive which does not damage, for example, paper and shaped items.
The coating composition according to the first embodiment of the present invention can be used in a large variety of applications, depending on the hardness, adherence, durability and curing conditions selected by the compounder. A pretty soft coating compounded for low adherence can be used as a plastifiable protective coating. A pretty soft coating compounded for high adherence can be used as a breakage preventive coating for carbonated beverage glass bottles. A pretty hard coating compounded for high adherence and long-term durability can be used as an artificial lawn or an anticorrosive coating for metals of an automobile, etc.
The sealant composition according to the first embodiment of the present invention can be used in a large variety of applications. It is most suitable for use as a gap filling agent for building. After the application, the sealant composition is baked (e.g., in a paint stove). This includes the use in automobile and appliance manufacture. Another suitable use of the sealant composition is in a gasket material, for example, caps of food and drink containers.
Asphalt is another customary material which is advantageous when used in combination with the epoxidized block copolymer according to the first embodiment of the present invention. The term xe2x80x9casphaltxe2x80x9d used herein means bituminous materials such as straight asphalt, cut back asphalt, blown asphalt, natural asphalt, tar pitch and petroleum pitch. These are used either individually or in combination. Compatible asphalt is suitable for use in the first embodiment of the present invention. The compatible asphalt is asphalt which provides a blend which does not suffer from phase separation even if it is allowed to stand still. The amount of asphalt used in the compound can be largely varied depending on the performance required in specified use. However, the asphalt is generally incorporated in the compound in an amount of 5 to 95% by weight, preferably, 5 to 90% by weight.
The inventors have made further intensive studies and as a result have found that the acid value of the epoxidized block copolymer exerts a substantial influence on the amount of formed gel. The second embodiment of the present invention has been completed on the basis of this finding.
Illustratively, the second embodiment of the present invention is directed to an epoxidized block copolymer obtained by epoxidizing a block copolymer comprising a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound and a polymer block (B) composed mainly of a conjugated diene compound or a product of hydrogenation of the block copolymer, this epoxidized block copolymer having an acid value of not greater than 10 mgKOH/g.
The term xe2x80x9cblock copolymerxe2x80x9d as used in the second embodiment of the present invention means the block copolymer comprising a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound and a polymer block (B) composed mainly of a conjugated diene compound. The term xe2x80x9cproduct of hydrogenation of the block copolymerxe2x80x9d means a polymer obtained by partially hydrogenating unsaturated carbon bonds contained in the polymer block (B) of the block copolymer through a hydrogenation reaction. The term xe2x80x9cepoxidized block copolymerxe2x80x9d as used in the second embodiment of the present invention means a polymer obtained by epoxidizing unsaturated carbon bonds contained in the polymer block (B) of the block copolymer or product of hydrogenation thereof.
Representative examples of the vinyl aromatic hydrocarbon compounds which can be employed in the formation of the block copolymer include styrene, various alkyl-substituted styrenes such as xcex1-styrenes, alkoxy-substituted styrenes, vinylnaphthalene, alkyl-substituted vinylnaphthalene, divinylbenzene and vinyltoluene. Of these, styrene is especially preferred. These can be used either individually or in combination. Representative examples of the conjugated diene compounds which can be employed in the formation of the block copolymer include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene and phenyl-1,3-butadiene. Of these, 1,3-butadiene and isoprene are preferred because these are inexpensive and readily available. The above compounds can be used either individually or in combination.
In the block copolymer, the vinyl aromatic hydrocarbon compound and conjugated diene compound which can be employed in the formation thereof are preferably used in a ratio of 5/95 to 70/30, still preferably, 10/90 to 60/40. The number average molecular weight of the block copolymer suitable for use in the present invention is preferred to range from 5000 to 60,000, especially, 10,000 to 50,000. When the molecular weight is lower, rubbery elastomer properties are hardly exhibited. On the other hand, when the molecular weight is higher, unfavorably the melting becomes difficult. Although the structure of the block copolymer is not particularly limited, it may be, for example, vinyl aromatic hydrocarbon compound/conjugated diene compound block copolymers represented by the formulae: A-B-A, B-A-B-A and A-B-A-B-A. The structure of the molecule per se thereof may be any of linear, branched and radial configurations or an arbitrary combination of these. The process for producing the unepoxidized block copolymer is not particularly limited and any known process can be used.
For example, the processes as described in Japanese Patent Publication Nos. 23798/1965, 3252/1972, 2423/1973 and 28925/1981 can be mentioned in which the production is carried out in the presence of, for example, a lithium catalyst in an inert solvent. The process for producing the block copolymer hydrogenation product is not particularly limited and any known process can be used.
For example, the processes as described in Japanese Patent Publication Nos. 8704/1967 and 6636/1968 can be mentioned in which the block copolymer is hydrogenated in the presence of a hydrogenation catalyst in an inert solvent. Although the degree of hydrogenation is not particularly limited, when the epoxidation reaction follows, it is required that unsaturated carbon bonds capable of reacting with the epbxidizing agent remain in the molecule of the hydrogenation product. The block copolymer or product of hydrogenation thereof is dissolved or slurried in an appropriate organic solvent and thereafter epoxidized. The site epoxidized by the epoxidizing agent is an unsaturated bond contained in the polymer block (B).
Representative examples of organic solvents suitable for use in the epoxidation include linear and branched hydrocarbons such as pentane, hexane, heptane and octane and alkyl-substituted derivatives thereof, alicyclic hydrocarbons such as cyclopentane, cyclohexane and cycloheptane and alkyl-substituted derivatives thereof, aromatic hydrocarbons such as benzene, naphthalene, toluene and xylene and alkyl-substituted derivatives thereof and aliphatic carboxylic acid esters such as methyl, ethyl and propyl acetates. Of these, the use of cyclohexane, ethyl acetate, chloroform, toluene, xylene and hexane is preferred from the viewpoint of the solubility of the block copolymer or product of hydrogenation thereof and the easiness of subsequent solvent recovery. Representative examples of epoxidizing agents which can be used in the epoxidation reaction include organic peracids such as peracetic acid, perbenzoic acid, performic acid and trifluoroperacetic acid, hydrogen peroxide and mixtures of hydrogen peroxide and low molecular fatty acids.
According to necessity, a catalyst can be used in the epoxidation. Of the above epoxidizing agents, peracetic acid is the most suitable because not only is it industrially produced in large quantity so that it can be procured at lowered cost but also its stability is relatively high. The amount of added epoxidizing agent is not particularly limited and can be arbitrarily selected depending on, for example, the reactivity of the epoxidizing agent, the desired degree of epoxidation and the amount of unsaturated carbon bonds contained in the employed block copolymer or product of hydrogenation thereof. The epoxidation reaction temperature is varied depending on the types and amounts of epoxidizing agent used, solvent used, block copolymer and product of hydrogenation thereof and is not particularly limited.
For example, when peracetic acid is used as the epoxidizing agent, the reaction temperature preferably ranges from 0 to 70xc2x0 C. When the reaction temperature is lower than 0xc2x0 C., the reaction rate is too low. On the other hand, when the reaction temperature exceeds 70xc2x0 C., unfavorably the formed epoxy ring is opened and decomposition of peracetic acid is promoted. For improving the stability of peracetic acid, a phosphate salt may be added to the reaction system prior to the epoxidation reaction. Thereafter, the solvent is removed and drying is performed, thereby recovering the epoxidized block copolymer.
The solvent removal can be effected by, for example, the method in which steam stripping is conducted in the presence of a surfactant or the method in which the solvent is directly removed by heating. The steam stripping method comprises stripping the solvent in the presence of a cationic, anionic, amphoteric or nonionic surfactant at a temperature which is not lower than the boiling point of the organic solvent or, when the organic solvent forms an azeotrope with water, the azeotropic temperature but not higher than 120xc2x0 C. to thereby obtain a slurry having crumbled polymer dispersed in the water. The direct solvent removing method comprises removing the solvent by the use of, for example, a vacuum dryer.
Thereafter, dehydration and drying are conducted to thereby obtain the epoxidized block copolymer. The methods of dehydration and drying are not particularly limited and any customary methods may be employed.
The second embodiment of the present invention is characterized in that the acid value of the above obtained epoxidized block copolymer is not greater than 10 mgKOH/g. Herein, the acid value of the epoxidized block copolymer is the weight of potassium hydroxide required to neutralize acids contained in 1 g of the epoxidized block copolymer obtained by performing the epoxidation reaction, solvent removal and drying, which weight is measured by titration. The acids are mainly formed as by-products in the epoxidation reaction. For example, when peracetic acid is used as the epoxidizing agent, acetic acid is formed as by-product in the epoxidation reaction.
Further, acids attributed to starting material impurities and to various additives used in the above production of epoxidized block copolymer are also included in the acid value referred to in the second embodiment of the present invention as long as the amount thereof is determined by titration with potassium hydroxide. When the acid value is higher than 10 mgKOH/g, the gel content of finally obtained epoxidized block copolymer is so high that the melt flow processability is deteriorated unfavorably.
In particular, when the acid value is too high in the melt kneading of the epoxidized block copolymer together with other resin or rubber at high temperatures, a large amount of gel is formed during the melt kneading, so that the moldability of the composition is gravely deteriorated. The acid value can be regulated to 10 mgKOH/g or below by neutralizing and/or washing with water the epoxidized block copolymer solution obtained by the epoxidation reaction to thereby remove acids. When steam stripping follows, not only is steam distillation of the solvent carried out but also the acids are dissolved in water and removed with the result that the epoxidized block copolymer with an especially low acid value can be obtained.
Representative examples of alkaline aqueous solutions which can be used in the above neutralization include aqueous solutions of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, calcium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium acetate, potassium acetate and ammonia. The above alkali is used in a molar amount required for neutralizing the acids which are present in the reaction mixture. When the amount of alkali is too large, the epoxy ring is opened unfavorably.
On the other hand, when the amount of alkali is too small, unfavorably acids remain and the gel content is increased to thereby deteriorate the properties of the epoxidized block copolymer. The water washing may be conducted either continuously or batchwise. In the batchwise washing, it is preferred that washing be repeated a few times with the use of 50 to 1000 parts by weight of water per 100 parts by weight of the crude reaction mixture resulting from the epoxidation.
In particular, when a large amount of epoxidizing agent is used, acids are incidentally formed in a large amount corresponding thereto. Thus, it is preferred that, for example, the frequency of washing be increased so as to achieve satisfactory removal of the acids. In the water washing, an inorganic salt such as sodium chloride or sodium sulfate may be added for achieving effective separation of the organic phase from the water phase.
The molecular weight distribution of the epoxidized block copolymer obtained in the second embodiment of the present invention is preferred to be 10 or below. The term xe2x80x9cmolecular weight distributionxe2x80x9d used herein means a ratio (Mw/Mn) of weight-average molecular weight (Mw) to number-average molecular weight (Mn) in terms of polystyrene as measured by GPC.
The molecular weight distribution is still preferably 5 or below and optimally 3 or below. When the molecular weight distribution is larger than 10, unfavorably, the melt flowability of the resin is gravely deteriorated to thereby cause poor moldability. It is likely that the greater the amount of formed gel, the larger the molecular weight distribution. According to necessity, the epoxidized block copolymer of the present invention can be blended with various additives, e.g., an age resister, a crosslinking agent, a thermal stabilizer, an ultraviolet absorber, an inorganic filler such as silica, talc or carbon, a plasticizer and a softening agent such as oil before use thereof.
The epoxidized block copolymer according to the second embodiment of the present invention has excellent moldability because of the properties attributed to its peculiar skeletal structure and the low content of gel. Thus, the epoxidized block copolymer can be used in the form of, for example, a thermoplastic resin composition, rubbery polymer composition, asphalt composition, adhesive composition, sealant composition or damping composition. Further, the epoxidized block copolymer can be used in a resin compatibilizer, an impact resistance improver, a latex, an emulsion and a resin filler.
The epoxidized block copolymer with a low gel content and excellent moldability can be obtained by reducing the acid value thereof. In this epoxidized block copolymer, the amount of formed gel is especially small during the melt kneading thereof by heating. Therefore, the epoxidized block copolymer can most suitably be used in a composition with a thermoplastic resin or rubbery polymer, an asphalt composition, an adhesive, a resin filler and the like.
The inventors have studied the method of obtaining the epoxidized block copolymer which is excellent in thermal stability and hue and as a result have found that the object can be attained by the addition of any of specified stabilizers. The third embodiment of the present invention has been completed on the basis of this finding.
Illustratively, the third embodiment of the present invention provides an epoxidized block copolymer composition which comprises 100 parts by weight of an epoxidized block copolymer (hereinafter may be referred to simply as xe2x80x9cpolymerxe2x80x9d) obtained by epoxidizing a block copolymer comprising a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound and a polymer block (B) composed mainly of a conjugated diene compound or a product of hydrogenation of the block copolymer and, added thereto, 0.005 to 10 parts by weight of a phenolic stabilizer and/or phosphorous stabilizer. Further, the third embodiment of the present invention provides the above defined epoxidized block copolymer composition in which the phenolic stabilizer is a member selected from the group consisting of tetrakis(methylene-3-(3xe2x80x2,5xe2x80x2-di-tert-butyl-4xe2x80x2-hydroxyphenyl)propionate)-methane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4xe2x80x2-hydroxybenzyl)benzene and 2,6-di-tert-butyl-4-methylphenol and in which the phosphorous stabilizer is a member selected from the group consisting of trisnonylphenyl phosphite and tris(2,5-di-tert-butylphenyl)phosphite.
The most characteristic feature of the third embodiment of the present invention resides in the addition of the phenolic stabilizer and/or phosphorous stabilizer to the epoxidized block copolymer for obtaining the epoxidized block copolymer which is excellent in thermal stability and hue. The addition of these stabilizers enables markedly suppressing the deterioration of the epoxidized block copolymer by heating.
Representative examples of phenolic stabilizers which can be used in the third embodiment of the present invention include tetrakis(methylene-3-(3xe2x80x2,5xe2x80x2-di-tert-butyl-4xe2x80x2-hydroxyphenyl)propionate)methane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4xe2x80x2-hydroxybenzyl)benzene, 2,6-di-tert-butyl-4-methylphenol, 4-hydroxymethyl-2,6-di-tert-butylphenol, 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, triethylene glycol bis(3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)-propionate), 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid, 2,2xe2x80x2-methylenebis(4-methyl-6-tert-butylphenol), 3,9-bis(2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, 2,6-di-tert-butyl-4-ethylphenol, butylated hydroxyanisole, 2,2xe2x80x2-dihydroxy-3,3xe2x80x2-dicyclohexyl-5,5xe2x80x2-dimethyldiphenylmethane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4xe2x80x2-butylidene-bis(6-tert-butyl-m-cresol), bis(3-cyclohexyl-2-hydroxy-5-methylphenyl)methane, 2,2xe2x80x2-methylenebis(4-ethyl-6-tert-butylphenol) and 1,1-methylenebis(2xe2x80x2-methyl-4xe2x80x2-hydroxy-5xe2x80x2-tert-butylphenyl)butane. These phenolic stabilizers can be used in combination.
Representative examples of phosphorous stabilizers which can be used in the third embodiment of the present invention include trisnonylphenyl phosphite, tris(2,5-di-tert-butylphenyl)phosphite, tris(2-di-tert-butylphenyl)phosphite and tris(2,4-bis(1,1-dimethylpropyl)phenyl)phosphite. These phosphorous stabilizers can be used in combination.
In the third embodiment of the present invention, the phenolic stabilizer and the phosphorous stabilizer may be used either independently or in combination. In the third embodiment of the present invention, the phenolic stabilizer and/or phosphorous stabilizer is added in an amount of 0.005 to 10 parts by weight, preferably, 0.05 to 3 parts by weight and, still preferably, 0.1 to 2 parts by weight in terms of the amount of each of the stabilizers per 100 parts by weight of epoxidized block copolymer. When the amount of added stabilizer is smaller than 0.005 part by weight, the thermal stability would be deteriorated. On the other hand, even when the amount is greater than 10 parts by weight, further thermal stability improving effect is trivial. Therefore, the use of stabilizer in such a large amount is not desired from the economic point of view. The time of addition of the stabilizer is not particularly limited and the stabilizer can be incorporated at any step before finally obtaining the epoxidized block copolymer. For example, the thermal stabilizer may be added to the organic solution or slurry of the epoxidized block copolymer prior to steam stripping. Also, the thermal stabilizer may be added simultaneously with the dehydration and drying of hydrous crumbe after steam stripping with the use of an extruder. Further, the thermal stabilizer may be kneaded into the dried polymer again with the use of a kneading extruder.
Sulfur and amine stabilizers having been conventionally used may be added to the copolymer composition of the third embodiment of the present invention. Further, according to necessity, the copolymer composition can be loaded with various additives, e.g., an age resister, a crosslinking agent, an ultraviolet absorber, an inorganic filler such as silica, talc, carbon or glass fiber, a plasticizer and a softening agent such as oil before use thereof. The time of addition thereof is not particularly limited and these can be incorporated at any step before finally obtaining the epoxidized block copolymer. The epoxidized block copolymer composition having excellent thermal stability obtained by the process according to the third embodiment of the present invention can be utilized not only as various molded items such as a sheet, a film, variously shaped injection moldings and a hollow shaped article but also as a modifier of various thermoplastic resins, a pressure sensitive adhesive, a raw material of adhesives, an asphalt improver and raw materials of household electric appliances, automobile parts, industrial parts, household goods and toys.
The third embodiment of the present invention enables providing the epoxidized block copolymer composition having excellent thermal stability and hue, which is prepared through epoxidation of the block copolymer comprising the polymer block (A) composed mainly of the vinyl aromatic hydrocarbon compound and the polymer block (B) composed mainly of the conjugated diene compound or the product of hydrogenation of the block copolymer.
The inventors have further made intensive studies and as a result have found that the mutually blocking properties can effectively be suppressed without detriment to the inherent properties of the epoxidized block copolymer by adding a specified compound. The fourth embodiment of the present invention has been completed on the basis of this finding.
Illustratively, the fourth embodiment of the present invention provides a composition which comprises 100 parts by weight of an epoxidized block copolymer (E) obtained by epoxidizing a block copolymer (C) comprising a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound and a polymer block (B) composed mainly of a conjugated diene compound or a product (D) of hydrogenation of the block copolymer and, added thereto, 0.001 to 5 parts by weight of an antiblocking agent.
The composition according to the fourth embodiment of the present invention is loaded with an antiblocking agent in an amount of 0.001 to 5 parts by weight, preferably, 0.01 to 2 parts by weight and, still preferably, 0.05 to 1 part by weight per 100 parts by weight of the epoxidized block copolymer (E) for inhibiting mutual blocking of the thus obtained epoxidized block copolymer (E). When the amount of added antiblocking agent is less than 0.001 part by weight, unfavorably, satisfactory antiblocking effect cannot be exerted. On the other hand, when the amount is greater than 5 parts by weight, also unfavorably, the inherent properties of the epoxidized block copolymer, especially, the transparency thereof, are gravely deteriorated although the blocking can be avoided. Mutual blocking of the obtained epoxidized block copolymer composition is substantially inhibited not only in the composition per se of powdery or pelletized form but also in various products of film or sheet form prepared therefrom.
Examples of antiblocking agents which can be used in the formation of the composition according to the fourth embodiment of the present invention include silicon compounds, fatty acid salts, fatty acid esters, fatty acid amides and nonionic surfactants. Representative examples of the silicon compounds include silicon oxide, silicone oil, silicon emulsion and other silicone fluids. The silicone fluids include alkyl, aryl and cycloalkyl-substituted silicone compounds having 0 to 12 carbon atoms per unit. Of these, silicon oxide and polydimethylsiloxane are especially preferred. It is preferred that silicon oxide have an average particle size ranging from 0.005 to 25 xcexcm.
In the fatty acid residue employed to constitute a fatty acid salt or fatty acid ester as the antiblocking agent, the number of carbon atoms per molecule is selected within the range of 10 to 20, preferably, 12 to 18. When the number of carbon atoms is less than 10 or greater than 20, unfavorably, satisfactory antiblocking effect cannot be exerted. Representative examples of the fatty acid salts include salts composed of metals belonging to Groups I, II, III and IV of the periodic table and acids such as lauric acid, myristic acid, palmitic acid, stearic acid and oleic acid. Of these, calcium stearate is especially preferred. Representative examples of the fatty acid esters include glycerol monostearate, glycerol distearate and glycerol tristearate. Glycerol monostearate is especially preferred. Both the fatty acid salts and fatty acid esters may be used either individually or in combination.
Representative examples of the fatty acid amides as the antiblocking agents include stearamide, oleamide and ethylenebisstearamide. Representative examples of the noionic surfactants as the antiblocking agents include sorbitan esters, propylene glycol fatty acid esters, sucrose fatty acid esters, citric acid mono(di or tri)stearates, pentaerythritol fatty acid esters, trimethylol fatty acid esters, polyglycerol fatty acid esters, polyoxyethylene glycerol fatty acid esters, polyesters, polyoxyethylene sorbitan fatty acid esters, polyethylene glycol fatty acid esters, polypropylene glycol fatty acid esters, polyoxyethylene glycol aliphatic alcohol ethers, polyoxyethylene alkylphenyl ethers, N,N-bis(2-hydroxyethylene) fatty amines, fatty acid/diethanol-amine condensates, polyoxyethylene/polyoxypropylene block polymers, polyethylene glycol and polypropylene glycol. Especially preferred nonionic surfactants are those having polyoxyethylene units, such as polyoxyethylene glycerol fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene aliphatic alcohol ethers, polyoxyethylene alkylphenyl ethers and polyoxyethylene/polyoxypropylene block polymers.
At least one member may be selected from each of the above antiblocking agent groups or, occasionally, at least two members may be selected therefrom and used in mixture in order to obtain the composition according to the fourth embodiment of the present invention. Also, members may be selected from a plurality of groups selected from the various antiblocking agent groups consisting of the silicon compound, fatty acid salt, fatty acid ester, fatty acid amide and nonionic surfactant groups and used in mixture.
With respect to the method of incorporating the antiblocking agent, it is preferred that the antiblocking agent be deposited on the surfaces of pellets of the epoxidized block copolymer (E) from the economic point of view. Examples of the methods include (1) the method in which the pellets are directly covered with the antiblocking agent, or the pellets are coated with the antiblocking agent and, according to necessity, dried; (2) the method in which the strand extruded through an extruder die is cut in water in which the antiblocking agent has been dissolved or suspended in advance and the obtained wet pellets are dried to thereby deposit the antiblocking agent on the pellet surface; and (3) the method in which the polymer (E) and the antiblocking agent are dryblended, and kneaded and pelletized by the use of a general-purpose extruder.
The epoxidized block copolymer composition according to the fourth embodiment of the present invention can be loaded with other various resin additives according to necessity. Examples of the other resin additives include an age resister, a crosslinking agent, a thermal stabilizer, an ultraviolet absorber, an inorganic filler such as silica, talc or carbon, a plasticizer and a softening agent such as oil.
The time of addition of these additives is not particularly limited and they can be incorporated at any step of the process of preparing the epoxidized block copolymer composition. For example, the thermal stabilizer may be added to the organic solution or slurry of the epoxidized block copolymer prior to steam stripping.
The epoxidized block copolymer composition obtained in the fourth embodiment of the present invention can be molded by the use of the molding technique for thermoplastic resins such as injection molding, extrusion molding, blow molding, compression molding or rotational molding into various products such as a sheet, a film, variously shaped injection moldings and a hollow shaped article. For example, the epoxidized block copolymer composition can be utilized not only as raw materials for molding of household electric appliances, automobile parts, industrial parts, household goods, toys and the like but also in a modifier of various thermoplastic resins, a pressure sensitive adhesive, a raw material of adhesives, an asphalt improver and the like.
The fourth embodiment of the present invention exerts the following especially advantageous effects and the value thereof is very high in industrial applications.
(1) The epoxidized block copolymer composition according to the fourth embodiment of the present invention has substantially suppressed mutually blocking properties, irrespective of the shape thereof. For example, the crumbs or pellets do not adhere to each other, and neither do the products prepared from this composition, e.g., films, sheets and other molded items.
(2) The epoxidized block copolymer composition according to the fourth embodiment of the present invention contains only a small amount of antiblocking agent, so that the transparency and other properties of the copolymer composition are not deteriorated.
The inventors have further made intensive studies and as a result have found that the epoxidized block copolymer can be recovered through a simple process without any economic problem by feeding the organic solvent solution of epoxidized block copolymer into an evaporator and directly evaporating off the organic solvent therein instead of the steam stripping method. The fifth embodiment of the present invention has been completed on the basis of this finding.
Illustratively, the fifth embodiment of the present invention provides a process for recovering an epoxidized block copolymer, the process comprising recovering an epoxidized block copolymer (E) obtained by epoxidizing in an organic solvent a block copolymer (C) comprising a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound and a polymer block (B) composed mainly of a conjugated diene compound or a product (D) of hydrogenation of the block copolymer from an organic solvent solution thereof, wherein the organic solvent solution is fed into an evaporator to thereby directly evaporate off the organic solvent. The epoxidized block copolymer which does not suffer from odor development and appearance defects such as foaming during the molding step can be provided by lowering the residual organic solvent content to not greater than 5000 ppm according to the above process.
The fifth embodiment of the present invention will now be described in detail.
The characteristic feature of the fifth embodiment of the present invention resides in that the obtained organic solvent solution of epoxidized block copolymer (E) is quantitatively fed by means of, for example, a pump into an evaporator, where the organic solvent is directly evaporated off from the organic solvent solution to thereby recover the epoxidized block copolymer (E). Examples of such evaporators include a flash vessel evaporator, an agitating vessel evaporator, a thin-film evaporator, a wetted wall column evaporator, a longitudinal screwed evaporator and a vented extruder which enable one-stage or at least two-stage, i.e., multi-stage concentration. At least two evaporators selected from among the above ones may be used in combination for increasing the production capacity. Of the evaporators, the use of a vented extruder is especially preferred from the viewpoint that the solvent removing capacity is large and that the amount of scorched resin is small.
The vented extruder preferably used in the practice of the fifth embodiment of the present invention will be described now. The vented extruder is one having at least one, preferably, 1 to 10 and, still preferably, 1 to 5 deairing vent parts. In the extruder, the number of screws is at least one, preferably, at least two. Of these, a vented twin-screw extruder is especially preferred from the viewpoint of the availability for general purposes.
With respect to the vented extruder of the above structure, it is preferred that L/D (L representing the length of screw and D the outer diameter of screw) range from about 2 to 50, especially, from about 4 to 40. It is no matter whether the screws are structured so as to engage with each other or not and whether they are corotating or counterrotating.
A vented twin-screw extruder having such a structure that a heating medium can be passed through the internal part of each screw is the most suitable among the available varieties. The extruder of this structure is preferred from the viewpoint that a large amount of heat taken away at the time of evaporation of the organic solvent can satisfactorily be supplemented by a heat supply. Further, an extruder having a continuous gas phase zone at the upper part of the inside of the extruder is preferred from the viewpoint of the efficiency of removal of the organic solvent.
The temperature and internal pressure of the evaporator are determined taking into account, for example, the processing capacity, the properties of polymer (viscosity, thermal stability, etc.), the type and concentration of the organic solvent and the quality of the product. It is preferred that the temperature of the evaporator range from 80 to 300xc2x0 C., especially, 120 to 250xc2x0 C. When the temperature of the evaporator is lower than 80xc2x0 C., removal of the organic solvent is not satisfactory. On the other hand, when it is higher than 300xc2x0 C., unfavorably a large amount of gel occurs in the polymer. The internal pressure of the evaporator is determined so as to be preferably not greater than 500 Torr, still preferably, within the range of from 1 to 400 Torr. The internal pressure of the evaporator means the pressure at a point exhibiting the lowest pressure in the gas phase zone brought into contact with the resin within the evaporator. With respect to the extruder, generally, the above internal pressure means the value read from a pressure gauge mounted to the vent part. When the internal pressure of the evaporator is higher than 500 Torr, unfavorably, the organic solvent cannot satisfactorily be removed. In the use of the vented extruder, the screw revolution speed ranges from 20 to 500 rpm, preferably, from 30 to 400 rpm.
It is preferred that the organic solvent be directly evaporated off by the above operation (hereinafter also referred to as the xe2x80x9cdirect solvent removalxe2x80x9d) so that the residual organic solvent content of the finally obtained epoxidized block copolymer is not greater than 5000 ppm, preferably, not greater than 2000 ppm and, still preferably, not greater than 1000 ppm. When the residual organic solvent content is greater than 5000 ppm, unfavorably foaming and odor development are invited in the molding of the epoxidized block copolymer into a product configuration. The residual organic solvent content can easily be regulated by changing the conditions such as the temperature of the evaporator, the internal pressure of the evaporator and the processing speed.
The epoxidized block copolymer having undergone the direct solvent removal by the evaporator can be obtained in the form of any of foamed crumbs, granules and powder and also can be obtained in the form of strands and pellets. Preferably, the epoxidized block copolymer is obtained in the form of pellets.
According to necessity, the epoxidized block copolymer according to the fifth embodiment of the present invention can be loaded with various additives, e.g., a thermal stabilizer, an age resister, a crosslinking agent, an ultraviolet absorber, an inorganic filler such as silica, talc or carbon, a plasticizer and a softening agent such as oil before use thereof. The time of addition thereof is not particularly limited and these can be incorporated at any step before finally obtaining the epoxidized block copolymer.
The epoxidized block copolymer obtained by the process according to the fifth embodiment of the present invention per se can be utilized not only as various molded items such as a sheet, a film, variously shaped injection moldings and a hollow shaped article but also as a modifier of various thermoplastic resins, a pressure sensitive adhesive, a raw material of adhesives, an asphalt improver and raw materials of household electric appliances, automobile parts, industrial parts, household goods and toys.
The fifth embodiment of the present invention enables recovering the epoxidized block copolymer (E) synthesized by epoxidizing in the organic solvent the block copolymer (C) comprising the polymer block (A) composed mainly of the vinyl aromatic hydrocarbon compound and the polymer block (B) composed mainly of the conjugated diene compound or the product (D) of hydrogenation of the block copolymer from the organic solvent solution thereof through the simple economic. process.
The inventors have still further studied the process for producing the epoxidized block copolymer and as a result have found that the above problems can be solved by conducting the first-stage concentration of the epoxidation reaction mixture with the use of an evaporator and the second-stage concentration with the use of a kneading evaporator (two-stage concentration) to thereby effect solvent removal. The sixth embodiment of the present invention has been completed on the basis of this finding.
Illustratively, the sixth embodiment of the present invention provides a process for producing an epoxidized block copolymer, which comprises the steps of:
mixing the block copolymer (C) comprising in its molecule not only a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound but also a polymer block (B) composed mainly of a conjugated diene compound or a product (D) of hydrogenation of the block copolymer with an organic solvent so as to obtain an organic solvent solution or organic solvent slurry (hereinafter the xe2x80x9csolutionxe2x80x9d may include the slurry) having a polymer concentration of 5 to 50% by weight;
conducting epoxidation with the use of an epoxidizing agent to thereby obtain an epoxidation reaction mixture;
feeding the epoxidation reaction mixture into an evaporator to thereby evaporate the organic solvent so that the epoxidation reaction mixture is concentrated; and
feeding the concentrate into a kneading evaporator to thereby remove the organic solvent. Moreover, the epoxidized block copolymer producing process is provided in which each of the evaporator and kneading evaporator is at a temperature of 80 to 300xc2x0 C. and an internal pressure of not greater than 500 Torr. Further, the epoxidized block copolymer producing process is provided in which the obtained epoxidized block copolymer (E) has an epoxy equivalent ranging from 140 to 2700. Still further, the epoxidized block copolymer producing process is provided in which the produced epoxidized block copolymer has a residual organic solvent concentration of not greater than 500 ppm. The sixth embodiment of the present invention will now be described in detail.
The sixth embodiment of the present invention is characterized in that the organic solvent is removed from the above obtained epoxidation reaction mixture containing the epoxidized block copolymer by means of a first evaporator (first-stage concentration) and then the remaining volatile component is distilled off by means of a second evaporator of the kneading type (second-stage concentration), so that the organic solvent can be evaporated off under condition such that the time of residence of polymer is short, i.e., the polymer having a residual organic solvent concentration of not greater than 500 ppm can be produced without suffering from long heat history.
Examples of evaporators which can be used in the first-stage concentration (first evaporators) in the sixth embodiment of the present invention include a shell and tube evaporator, a liquid film evaporator, a centrifugal thin-film evaporator and a plate evaporator. Of these, a shell and tube evaporator, a centrifugal thin-film evaporator and a plate evaporator are preferred. These have a large surface brought into contact with the epoxidation reaction mixture and are suitable for use in the concentration conducted at a high solvent content. The first-stage concentration is conducted so that the organic solvent content (volatile component content) ranges from 5 to 70% by weight, preferably, from 20 to 30% by weight. The use of the first evaporator enables reducing the size of the second evaporator.
Examples of kneading evaporators which can be used in the second-stage concentration (second evaporators) include a twin-screw evaporator of the surface renewing, self-cleaning type and a vented extruder each having kneading shafts. For realizing a large heating surface area, it is preferred to employ a kneading evaporator in which a heating medium can be passed through the internal part of each screw. The kneading evaporator with this structure can satisfactorily supply a large amount of heat required for evaporating the organic solvent. Further, this kneading evaporator is especially preferred from the viewpoint that the piston flow properties free of back mixing are exhibited to thereby ensure excellent blending performance and that the evaporation surface area can be large. With respect to the structure of the kneading evaporator, it is preferred that L/D (L representing the length of screw and D the outer diameter of screw) range from about 2 to 50, especially, from about 4 to 40. It is no matter whether the screws are structured so as to engage with each other or not and whether they are corotating or counterrotating. The kneading evaporator enables stably removing the organic solvent even from the epoxidation reaction mixture whose viscosity has increased because in the reduction of the organic solvent concentration.
Oil and other heating media, steam and an electrical heater can be used as the heating source for each evaporator.
In a practical mode of the epoxidized block copolymer producing process according to the sixth embodiment of the present invention, first, the epoxidation reaction mixture is continuously fed by means of a gear pump into the first evaporator, in which the solvent is distilled off within a flash tank at heating temperature not lower than the boiling point of the solvent. The epoxidation reaction mixture may be one washed with water in advance. The water washing may be conducted either continuously or batchwise. In the batchwise washing, it is preferred that washing be repeated a few times with the use of 50 to 1000 parts by weight of water per 100 parts by weight of the crude reaction mixture resulting from the epoxidation.
The organic solvent contained in large quantity in the epoxidation reaction mixture can easily be removed by conducting heating evaporation in the first evaporator.
In the sixth embodiment of the present invention, the volatile component is distilled off from the concentrate obtained by evaporation by means of the first evaporator with the use of the second evaporator to thereby separate the epoxidized block copolymer from the organic solvent. Distilling off the volatile component with the use of the second evaporator enables stably evaporating the organic solvent remaining in the concentrate under condition such that the time of residence of concentrate is short, i.e., the epoxidized block copolymer can be produced without suffering from long heat history.
The obtained epoxidized block copolymer can be extrusion molded in the customary manner into any form selected from among those of strands, pellets, foamed crumbs, granules and powder, preferably, into the form of pellets.
The internal temperature and internal pressure of each of the evaporator and the kneading evaporator are determined taking into account, for example, the processing capacity, the properties of polymer (viscosity, thermal stability, etc.), the type and concentration of the solvent and the quality of the product. It is preferred that the internal temperature of each of both the evaporators range from 80 to 300xc2x0 C., especially, 120 to 250xc2x0 C. When the internal temperature of the evaporator is lower than 80xc2x0 C., the viscosity is increased with the result that removal of the organic solvent becomes difficult unless the degree of pressure reduction is raised. On the other hand, when it is higher than 300xc2x0 C., unfavorably gelation occurs in the polymer. In particular, when the epoxidized block copolymer remains in the evaporator with the result of occurrence of a large amount of gel, unfavorably not only is the melt viscosity too high but also fisheyes are likely to occur in the product to thereby cause molding defects. The gel content is preferred to be not greater than 5% by weight, especially, not greater than 3% by weight and, still especially, not greater than 1% by weight. The gel content is expressed as the weight percentage of insolubles in tetrahydrofuran (THF).
The internal pressure of each evaporator is determined so as to be preferably not greater than 500 Torr, still preferably, within the range of from 1 to 400 Torr. When the internal pressure of the evaporator is higher than 500 Torr, unfavorably, the solvent cannot satisfactorily be removed.
It is preferred that the residual organic solvent content of the finally obtained epoxidized block copolymer be not greater than 5,000 ppm, preferably, not greater than 2000 ppm, still preferably, not greater than 1000 ppm and, most especially, not greater than 500 ppm. When the residual organic solvent content is too high, foaming and odor development are invited in the molding of the epoxidized-block copolymer unfavorably.
According to necessity, the epoxidized block copolymer according to the sixth embodiment of the present invention can be blended with various additives, e.g., a thermal stabilizer, an age resister, a crosslinking agent, an ultraviolet absorber, an inorganic filler such as silica, talc or carbon, a plasticizer and a softening agent such as oil before use thereof. The time of addition thereof is not particularly limited and the additives can be incorporated at any time before finally obtaining the epoxidized block copolymer.
The epoxidized block copolymer obtained by the process according to the sixth embodiment of the present invention is suitable for use in modifiers or modifier auxiliaries for rubbery or resinous polymers, adhesives, sealants, asphalt improvers and the like.
The sixth embodiment of the present invention enables separating the epoxidized block copolymer from the organic solvent without causing the epoxidized block copolymer to suffer from long-time heat history to thereby obtain the epoxidized block copolymer whose heat deterioration is trivial by removing the organic solvent from the epoxidation reaction mixture through the two-stage concentration.
The inventors have still further studied the direct removal of the solvent from the epoxidation reaction mixture and as a result have found that the epoxidized block copolymer having excellent thermal stability can be easily obtained at lowered cost by mixing a specified stabilizer with the epoxidation reaction mixture and then removing the organic solvent. The seventh embodiment of the present invention has been completed on the basis of this finding.
Illustratively, the seventh embodiment of the present invention provides a process for producing an epoxidized block copolymer, which comprises the steps of:
epoxidizing in an organic solvent a block copolymer (C) comprising a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound and a polymer block (B) composed mainly of a conjugated diene compound or a product (D) of hydrogenation of the block copolymer to thereby obtain an epoxidation reaction mixture containing an epoxidized block copolymer (E);
adding a phenolic stabilizer and/or a phosphorous stabilizer to the epoxidation reaction mixture in an amount of 0.005 to 5 parts by weight per 100 parts by weight of finally obtained epoxidized block copolymer; and
removing the organic solvent from the epoxidation reaction mixture. Further, the epoxidized block copolymer producing process is provided in which the organic solvent is directly evaporated off from the epoxidation reaction mixture having the phenolic stabilizer and/or phosphorous stabilizer added thereto. Still further, the epoxidized block copolymer producing process is provided in which, after the removal of the organic solvent, the epoxidized block copolymer has a residual organic solvent content of not greater than 5000 ppm. The seventh embodiment of the present invention will now be described in detail.
The characteristic feature of the seventh embodiment of the present invention resides in that the obtained epoxidation reaction mixture containing the epoxidized block copolymer (E) is quantitatively fed by means of, for example, a pump into an evaporator, then a phenolic stabilizer and/or a phosphorous stabilizer is added to the epoxidation reaction mixture and finally the organic solvent is directly evaporated off from the epoxidation reaction mixture. The epoxidized block copolymer (E) obtained in the above manner exhibits a markedly improved thermal stability, has a less tendency for gelation even if allowed to stand still at high temperature and enables marked suppression of a hue deterioration. Moreover, for adding a stabilizer to a plastic or rubber, it is generally needed to knead the stabilizer into the copolymer by the use of a device such as a kneading extruder. However, in the above method according to the seventh embodiment of the present invention, it is only needed to put the stabilizer in the epoxidation reaction mixture containing the epoxidized block copolymer (E) and thus it is not needed to conduct kneading of the stabilizer. This ensures operational and economic advantages.
Representative examples of phenolic stabilizers which can be used in the seventh embodiment of the present invention include tetrakis(methylene-3-(3xe2x80x2,5xe2x80x2-di-tert-butyl-4xe2x80x2-hydroxyphenyl)propionate)methane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4xe2x80x2-hydroxybenzyl)benzene, 2,6-di-tert-butyl-4-methylphenol, 4-hydroxymethyl-2,6-di-tert-butylphenol, 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, triethylene glycol bis(3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)-propionate), 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid, 2,2xe2x80x2-methylenebis(4-methyl-6-tert-butylphenol), 3,9-bis(2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, 2,6-di-tert-butyl-4-ethylphenol, butylated hydroxyanisole, 2,2xe2x80x2-dihydroxy-3,3xe2x80x2-dicyclohexyl-5,5xe2x80x2-dimethyldiphenylmethane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4xe2x80x2-butylidene-bis(6-tert-butyl-m-cresol), bis(3-cyclohexyl-2-hydroxy-5-methylphenyl)methane, 2,2xe2x80x2-methylenebis(4-ethyl-6-tert-butylphenol) and 1,1-methylenebis(2xe2x80x2-methyl-4xe2x80x2-hydroxy-5xe2x80x2-tert-butylphenyl)butane. Of these, tetrakis(methylene-3-(3xe2x80x2,5xe2x80x2-di-tert-butyl-4xe2x80x2-hydroxyphenyl)propionate)methane and 2,6-di-tert-butyl-4-methylphenol are preferred. The above phenolic stabilizers can be used in combination.
Representative examples of phosphorous stabilizers which can be used in the seventh embodiment of the present invention include trisnonylphenyl phosphite, tris(2,5-di-tert-butylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite and tris(2,4-bis(1,1-dimethylpropyl)phenyl)phosphite. These phosphorous stabilizers can be used in combination.
In the seventh embodiment of the present invention, the phenolic stabilizer and the phosphorous stabilizer may be used either independently or in combination. The phenolic stabilizer and/or phosphorous stabilizer is added in an amount of 0.005 to 5 parts by weight, preferably, 0.05 to 3 parts by weight and, still preferably, 0.1 to 2 parts by weight per 100 parts by weight of epoxidized block copolymer finally obtained after the removal of the solvent. The amount of stabilizer to be added to the epoxidation reaction mixture can be easily calculated from the concentration of block copolymer in the mixture and from the desired concentration. When the amount of added stabilizer is smaller than 0.005 part by weight, the thermal stability would be deteriorated. On the other hand, even when the amount is greater than 5 parts by weight, further thermal stability improving effect is trivial. Therefore, the use of stabilizer in such a large amount is not desired from the economic point of view.
Examples of evaporators which can be used in the seventh embodiment of the present invention include a flash vessel evaporator, an agitating vessel evaporator, a thin-film evaporator, a wetted wall column evaporator, a longitudinal screwed evaporator and a vented extruder which enable one-stage or at least two-stage, i.e., multi-stage concentration. At least two evaporators selected from among the above may be used in combination for increasing the production capacity. Of the evaporators, the use of a vented extruder is especially preferred from the viewpoint that the solvent removing capacity is large and that the amount of scorched resin is small.
The vented extruder preferably used in the practice of the seventh embodiment of the present invention will be described now.
The vented extruder is one having at least one, preferably, 1 to 10 and, still preferably, 1 to 5 deairing vent parts. In the extruder, the number of screws is at least one, preferably, at least two. Of these, a vented twin-screw extruder is especially preferred from the viewpoint of the availability for general purposes. With respect to the vented extruder of the above structure, it is preferred that L/D (L representing the length of screw and D the outer diameter of screw) range from about 2 to 50, especially, from about 4 to 40. It is no matter whether the screws are structured so as to engage with each other or not and whether they are corotating or counterrotating.
A vented twin-screw extruder having such a structure that a heating medium can be passed through the internal part of each screw is the most suitable among the available varieties. The extruder of this structure is preferred from the viewpoint that a large amount of heat taken away at the time of evaporation of the organic solvent can satisfactorily be supplemented by a heat supply. Further, an extruder having a continuous gas phase zone at the upper part of the inside of the extruder is preferred from the viewpoint of the efficiency of removal of the organic solvent.
The internal temperature and internal pressure of the evaporator are determined taking into account, for example, the processing capacity, the properties of polymer (viscosity, thermal stability, etc.), the type and concentration of the organic solvent and the quality of the product. It is preferred that the internal temperature of the evaporator range from 80 to 300xc2x0 C., especially, 120 to 250xc2x0 C. When the internal temperature of the evaporator is lower than 80xc2x0 C., removal of the organic solvent is not satisfactory. On the other hand, when it is higher than 300xc2x0 C., a large amount of gel occurs in the polymer unfavorably. In particular, when the epoxidized block copolymer remains in the evaporator at high temperature with the result of occurrence of a large amount of gel, unfavorably not only is the melt viscosity too high but also fisheyes are likely to occur to thereby cause molding defects. The gel content is preferred to be not greater than 5% by weight, especially, not greater than 3% by weight and, still especially, not greater than 1% by weight.
The internal pressure of the evaporator is determined so as to be preferably not greater than 500 Torr, still preferably, within the range of from 1 to 400 Torr. The internal pressure of the evaporator means the pressure at a point exhibiting the lowest pressure in the gas phase zone brought into contact with the resin within the evaporator. With respect to the extruder, generally, the above internal pressure means the value read from a pressure gauge mounted to the vent part. When the internal pressure of the evaporator is higher than 500 Torr, unfavorably, the organic solvent cannot satisfactorily be removed. In the use of the vented extruder, the screw revolution speed ranges from 20 to 500 rpm, preferably, from 30 to 400 rpm.
It is preferred that the organic solvent be directly evaporated off from the epoxidation reaction mixture so that the residual organic solvent content of the finally obtained epoxidized block copolymer is not greater than 5000 ppm, especially, not greater than 2000 ppm, still especially, not greater than 1000 ppm and, optimally, not greater than 500 ppm. When the residual organic solvent content is greater than 5000 ppm, unfavorably foaming and odor development are invited in the molding of the epoxidized block copolymer into a product configuration. The residual organic solvent content can easily be regulated by changing the conditions such as the temperature of the evaporator, the internal pressure of the evaporator and the processing speed.
The epoxidized block copolymer having undergone the direct solvent removal by the evaporator can be obtained in any form selected from among strands, pellets, foamed crumbs, granules and powder. Preferably, the epoxidized block copolymer is obtained in the form of pellets.
According to necessity, the epoxidized block copolymer according to the seventh embodiment of the present invention can be loaded with various additives, e.g., a thermal stabilizer, an age resister, a crosslinking agent, an ultraviolet absorber, an inorganic filler such as silica, talc or carbon, a plasticizer and a softening agent such as oil before use thereof. The time of addition thereof is not particularly limited and these can be incorporated at any step before finally obtaining the epoxidized block copolymer.
The epoxidized block copolymer obtained by the process according to the seventh embodiment of the present invention can be utilized not only as various molded items such as a sheet, a film, variously shaped injection moldings and a hollow shaped article but also as a modifier of various thermoplastic resins, a pressure sensitive adhesive, a raw material of adhesives, an asphalt improver and raw materials of household electric appliances, automobile parts, industrial parts, household goods and toys.
The seventh embodiment of the present invention enables producing the epoxidized block copolymer of excellent hue in which the amount of gel formed is trivial at heating by the economically advantageous process.
The inventors have further made intensive studies and as a result have found that the object can be attained by specified steps including a step in which the organic solvent is directly removed from the epoxidation reaction mixture in the process for producing the epoxidized block copolymer. The eighth embodiment of the present invention has been completed on the basis of this finding.
Illustratively, the eighth embodiment of the present invention provides a process for producing an epoxidized block copolymer (E) through epoxidation of a block copolymer (C) comprising a polymer block (A) composed mainly of a vinyl aromatic hydrocarbon compound and a polymer block (B) composed mainly of a conjugated diene compound or a product (D) of hydrogenation of the block copolymer, which process comprises the steps of:
(1) mixing the block copolymer (C) or product (D) of hydrogenation thereof with an organic solvent so as to obtain an organic solvent solution or organic solvent slurry having a polymer concentration of 5 to 50% by weight (hereinafter may be referred to simply as the xe2x80x9corganic solvent solutionxe2x80x9d);
(2) epoxidizing unsaturated carbon bonds contained in the polymer block (B) with the use of an epoxidizing agent in the organic solvent solution or organic solvent slurry to thereby obtain a reaction mixture;
(3) washing with water and/or neutralizing the epoxidation reaction solution or slurry obtained in the step (2) (hereinafter may be referred to simply as the xe2x80x9cepoxidation reaction mixturexe2x80x9d) so that the acid value of the epoxidation reaction mixture does not exceed 5 mgKOH/g; and
(4) feeding the epoxidation reaction mixture having undergone the water washing and/or neutralization into an evaporator to thereby directly evaporate off the organic solvent, so that an epoxidized block copolymer (E) is obtained whose residual organic solvent content is not greater than 5000 ppm and whose gel content is not greater than 5% by weight.
Further, the epoxidized block copolymer producing process is provided in which the epoxy equivalent of the epoxidized block copolymer (E) ranges from 140 to 2700. The eighth embodiment of the present invention will now be described in detail.
In the eighth embodiment of the present invention, the produced block copolymer (C) or product (D) of hydrogenation thereof is subjected to the following first to fourth steps to thereby obtain the epoxidized block copolymer.
In the first step according to the eighth embodiment of the present invention, an organic solvent is mixed with the block copolymer (C) or product (D) of hydrogenation thereof so as to obtain an organic solvent solution having a polymer concentration of 5 to 50% by weight. Representative examples of suitable organic solvents include linear and branched hydrocarbons such as pentane, hexane, heptane and octane and alkyl-substituted derivatives thereof, alicyclic hydrocarbons such as cyclopentane, cyclohexane and cycloheptane and alkyl-substituted derivatives thereof, aromatic hydrocarbons such as benzene, naphthalene, toluene and xylene and alkyl-substituted derivatives thereof, aliphatic carboxylic acid esters such as methyl, ethyl and propyl acetates and halogenated hydrocarbons such as chloroform. Of these, the use of cyclohexane, ethyl acetate, chloroform, toluene, xylene and hexane is preferred from the viewpoint of the solubility of the block copolymer (C) or product (D) of hydrogenation thereof and the easiness of subsequent solvent recovery.
When the concentration of the block copolymer (C) or product (D) of hydrogenation thereof is lower than 5% by weight, actually a too large amount of solvent must be used to an economic disadvantage. On the other hand, when the concentration is higher than 50% by weight, the solution viscosity is unfavorably too high, so that the mixing of the epoxidizing agent and the organic solvent solution or slurry is unsatisfactory in the second step and that removal of the reaction heat is difficult.
In the second step of the eighth embodiment of the present invention, unsaturated bonds present in the polymer block (B) contained in the organic solvent solution are epoxidized with an epoxidizing agent.
The epoxidation of the block copolymer (C) or product (D) of hydrogenation thereof can be performed by a reaction with, for example, an organic peracid.
Examples of epoxidizing agents which can be used in the epoxidation reaction include organic peracids such as peracetic acid, perbenzoic acid, performic acid and trifluoroperacetic acid, hydrogen peroxide and mixtures of hydrogen peroxide and low molecular fatty acids. Of these, peracetic acid is the most suitable epoxidizing agent because not only is it industrially produced in large quantity so that it can be obtained at lowered cost but also its stability is relatively high. A catalyst can be used in the epoxidation according to necessity.
The epoxidation reaction temperature is varied depending on, for example, the employed epoxidizing agent, the employed organic solvent and the type and amount of block copolymer or hydrogenation product thereof and is not particularly limited. For example, when peracetic acid is used as the epoxidizing agent, the reaction temperature preferably ranges from 0 to 70xc2x0 C. When the reaction temperature is lower than 0xc2x0 C., the reaction rate is too low. On the other hand, when the reaction temperature exceeds 70xc2x0 C., unfavorably the formed epoxy ring is opened and decomposition of peracetic acid is promoted. For improving the stability of peracetic acid, a phosphate salt may be added to the reaction system prior to the epoxidation reaction. From the viewpoint of productivity, it is preferred that the epoxidation reaction time be selected within the range of 0.1 to 72 hr, especially, 0.2 to 10 hr.
In the third step of the eighth embodiment of the present invention, the epoxidation reaction mixture is washed with water and/or neutralized so that the acid value of the reaction mixture does not exceed 5 mgKOH/g. Herein, the acid value is the weight of potassium hydroxide required to neutralize acids contained in 1 g of the crude reaction mixture resulting from the epoxidation reaction, which weight is measured by titration.
The purpose of the water washing and/or neutralization is to remove acids and other by-products incidentally formed by the epoxidation reaction carried out in the preceding step. When the acid value is higher than 5 mgKOH/g, unfavorably, the epoxy ring of the epoxidized block copolymer is opened and the properties of the epoxidized block copolymer are deteriorated.
The water washing may be conducted either continuously or batchwise. In the batchwise washing, it is preferred that washing be repeated a few times with the use of 50 to 1000 parts by weight of water per 100 parts by weight of the crude reaction mixture resulting from the epoxidation. In particular, when a large amount of epoxidizing agent is used, acids are incidentally formed in a large amount corresponding thereto. Thus, it is preferred that, for example, the frequency of washing be increased so as to achieve satisfactory removal of the acids. In the water washing, an inorganic salt such as sodium chloride or sodium sulfate may be added for achieving effective separation of the organic phase from the water phase. Representative examples of alkaline aqueous solutions which can be used in the above neutralization include aqueous solutions of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, calcium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium acetate and potassium acetate. The above alkali is used in a molar amount required for neutralizing the acids which are present in the reaction mixture. When the amount of alkali is too large, unfavorably the epoxy ring is opened. On the other hand, when the amount of alkali is too small, unfavorably acids remain so as to cause deterioration leading to poor properties. For suppressing the opening of epoxy ring caused by exothermic neutralization, it is preferred that the neutralization be conducted while cooling the crude reaction mixture.
In the fourth step of the eighth embodiment of the present invention, the obtained epoxidation reaction mixture containing the epoxidized block copolymer (E) is quantitatively fed by means of, for example, a pump into an evaporator, where the organic solvent is directly evaporated off from the reaction mixture to thereby recover the epoxidized block copolymer.
Examples of evaporators which can be used in the eighth embodiment of the present invention include a flash vessel evaporator, an agitating vessel evaporator, a thin-film evaporator, a wetted wall column evaporator, a longitudinal screwed evaporator and a vented extruder which enable one-stage or at least two-stage, i.e., multi-stage concentration. At least two evaporators selected from among the above can be used in combination for increasing the production capacity. Of the evaporators, the use of a vented extruder is especially preferred from the viewpoint that the solvent removing capacity is large and that the amount of scorched resin is small.
The vented extruder preferably used in the practice of the eighth embodiment of the present invention will now be described in detail.
The vented extruder is preferred to have at least one, especially, 1 to 10 and, still especially, 1 to 5 deairing vent parts. In the extruder, the number of screws is preferred to be at least one, especially, at least two. Of these, a vented twin-screw extruder is especially preferred from the viewpoint of the availability for general purposes. With respect to the vented extruder of the above structure, it is preferred that L/D (L representing the length of screw and D the outer diameter of screw) range from about 2 to 50, especially, from about 4 to 40. It is no matter whether the screws are structured so as to engage with each other or not and whether they are corotating or counterrotating.
A vented twin-screw extruder having such a structure that a heating medium can be passed through the internal part of each screw is the most suitable among the available varieties. The extruder of this structure is preferred from the viewpoint that a large amount of heat taken away at the time of evaporation of the organic solvent can satisfactorily be supplemented by a heat supply. Further, an extruder having a continuous gas phase zone at the upper part of the inside of the extruder is preferred from the viewpoint that the efficiency of removal of the solvent is high.
The internal temperature and internal pressure of the evaporator are determined taking into account, for example, the processing capacity, the properties of polymer (viscosity, thermal stability, etc.), the type and concentration of the solvent and the quality of the product. It is preferred that the internal temperature of the evaporator range from 80 to 300xc2x0 C., especially, 120 to 250xc2x0 C. When the internal temperature of the evaporator is lower than 80xc2x0 C., removal of the organic solvent is not satisfactory to thereby cause low viscosity. On the other hand, when it is higher than 300xc2x0 C., a large amount of gel occurs in the polymer unfavorably. In particular, when the epoxidized block copolymer remains in the evaporator used in the fourth step at high temperatures with the result of occurrence of a large amount of gel, unfavorably not only is the melt viscosity too high but also fisheyes are likely to occur to thereby cause molding defects. The gel content is preferred to be not greater than 5% by weight, especially, not greater than 3% by weight and, still especially, not greater than 1% by weight.
The internal pressure of the evaporator is determined so as to be preferably not greater than 500 Torr, still preferably, within the range of from 1 to 400 Torr. The internal pressure of the evaporator means the pressure at a point exhibiting the lowest pressure in the gas phase zone brought into contact with the resin within the evaporator. With respect to the extruder, generally, the above internal pressure means the value read from a pressure gauge mounted to the vent part. When the internal pressure of the evaporator is higher than 500 Torr, unfavorably, the organic solvent cannot satisfactorily be removed. In the use of the vented extruder, the screw revolution speed ranges from 20 to 500 rpm, preferably, from 30 to 400 rpm.
It is preferred that the organic solvent be directly evaporated off from the epoxidation reaction mixture by the above operation (hereinafter also referred to as the xe2x80x9cdirect solvent removalxe2x80x9d) so that the residual organic solvent content of the finally obtained epoxidized block copolymer is not greater than 5000 ppm, especially, not greater than 2000 ppm, still especially, not greater than 1000 ppm and, optimally, not greater than 500 ppm. When the residual organic solvent content is greater than 5000 ppm, foaming and odor development are invited in the molding of the epoxidized block copolymer into a product configuration unfavorably. The residual organic solvent content can easily be regulated by changing the conditions such as the temperature of the evaporator, the internal pressure of the evaporator and the processing speed.
The epoxidized block copolymer having undergone the direct solvent removal by the evaporator can be obtained in any form selected from among strands, pellets, foamed crumbs, granules and powder. Preferably, the epoxidized block copolymer is obtained in the form of pellets.
According to necessity, the epoxidized block copolymer according to the eighth embodiment of the present invention can be loaded with various additives, e.g., a thermal stabilizer, an age resister, a crosslinking agent, an ultraviolet absorber, an inorganic filler such as silica, talc or carbon, a plasticizer and a softening agent such as oil before use thereof. The time of addition thereof is not particularly limited and these can be incorporated at any step before finally obtaining the epoxidized block copolymer.
The epoxidized block copolymer obtained by the process according to the eighth embodiment of the present invention can be utilized not only as various molded items such as a sheet, a film, variously shaped injection moldings and a hollow shaped article but also as a modifier of various thermoplastic resins, a pressure sensitive adhesive, a raw material of adhesives, an asphalt improver and raw materials of household electric appliances, automobile parts, industrial parts, household goods and toys.
The eighth embodiment of the present invention provides the economic and simple process comprising the above combination of four specified steps, which process enables producing the epoxidized block copolymer (E) whose residual organic solvent content and gel content are small by epoxidizing the block copolymer (C) comprising the polymer block (A) composed mainly of the vinyl aromatic hydrocarbon compound and the polymer block (B) composed mainly of the conjugated diene compound or the product (D) of hydrogenation of the block copolymer.